"Is it serious?" My first reaction is, "Jesus H Christ. You're Goddamn right it is", but I don't know your work environment, etc.--did you even wear a Covid-type mask, or a neckerchief, were you cutting/handling fiberglass constantly for 40hr/2.5/"4" years, were there fans blowing ('glass) at you, on and on. There's no way to tell how "serious" this is--how much your exposure has affected you can only be determined by a pulmonary function test and other lung tests. After you take them, a qualified doctor/specialist will read your results and determine exactly what you've "suffered".
(This IS the internet. Everything I've written and recommended could be pure bullshit [in your case alone] through some miraculous job site conditions that work in your health's favor. But from personal experience observing co-workers' deteriorating health as they got to their late 40s and early 50s in an auto body shop, I doubt it. They were all affected (and me, probably, too, despite my clean tests); but I quit the industry at age 37, on the spot at 10:47am on the day OSHA warned my dealership, once I found out the owner's stance on our health. Unlike you, I didn't give a damn what my co-workers "thought". A couple assholes (truly; I always regarded them as 'the enemy') were even pissed off with jealousy [THAT, I enjoyed; it was the only time they spoke I enjoyed hearing what they had to say]--"you can't quit; what are you gonna do for money??" like they gave a shit. I stayed poor for 3 years recovering economically while changing careers--so poor, my wife spent her childhood coin collection during our lean years. I mention this because you might ponder a similar career move. It's gonna take some serious personal reflection.)
I think one thing's absolutely sure. Your lungs don't resemble a 31-year old office worker's lungs, and if you smoke, quit. Science has proven the smoking habit absolutely accelerates lung disease in asbestos and fiberglass -related afflictions. Hell, I could be wrong. It could be that your exposure was minimal because your description of your actual fiberglass handling is inaccurate enough that you're more like a weekend-homeowner-Xtimes/year-project-worker and have only minimal exposure--but by your description, your clothes and your car don't say that.
There's a chance you got less exposure than a "normal" unprotected fiberglass worker because of certain idiosyncrasies in your work environment, but "less" ain't 'none'. So much for all the sugar-coating...
You're worse off than if you had been smoking for "2.5/4" years that's for sure--some people by their longevity have proven their lungs can take "smoking"--George Burns, the comedian, instantly comes to mind and there are other unnamed anecdotal pack-a-day smokers who've made the news living to their 90s. On the other hand, David Janssen died at 48 (and looked 58) because he, too, used his lungs for chimneys. But in these cases, a chemical vulnerability causes the troubles- with fiberglass, it's all "synthetic abrasive degeneration"; certain lucky peoples' bodies may cope with tar and nicotine, but 'glass ain't a chemical. I digress...
Has/will this affect your life? Most probably. "I'm going to die young from this?" My answer is, if the gods who've determined the date of your passing have a "natural death" intended for you, then you've shortened their plans much like the average smoker has-- you've probably cut years off your life--how many, who can say. Most likely, with "only" 4 years exposure, you've got at least 25-40 years left if there are no other contributing factors (like a genetic predisposition for lung-related weaknesses, or smoking) and oncology technology is constantly improving. A LOT can happen between today and the "end of your life" so long as you don't get hit by a truck.
1) I stand by my best efforts to give you advice-- if you're a believer, apply for as much life insurance as possible and lock your insurance contract BEFORE YOU GET ANY MEDICAL EVALUATION. At 31 years, insurance companies drool over theoretical long-term potential subscribers as yourself so the rates are VERY cheap since you're *very* young by life insurance actuary tables. If you panic and get your (irregular) medical results recorded before applying for the insurance you'll either disqualify yourself or cause the rates to go up by *BIG* TENS of thousands of dollars over your next 25 years and beyond. Think "double or triple the rates" if you qualify as a theoretical estimated "47-year old subject".
You'd be a complete fuck-up to ignore advice #1 because you panicked first (even after reading all everyone's posted in this thread) and disqualify yourself from life insurance (and have a family [later] to support).
2) If for some reason you don't get out of the industry, immediately get a TC-23C respirator and a box of filters. Consider the manufacturer's standard-- a box of filters lasts 40 hours. Some hard-sell companies will claim the filters last until breathing through them is "labored". You've got one set of lungs; what you do to protect them is your business. In either example, the manufacturers don't claim that man-made synthetic filters are permanently effective. Think about that; in a roundabout way, it implies that your lungs don't have the resistance of a 40-hour filter against airborne particulates .
3) Get the medical tests as I described and establish your own pulmonary baselines AFTER the insurance play. DON'T PANIC. WHAT'S DONE IS DONE. Now, in this "immediacy", knowing as a fact how much your body has suffered isn't as important as planning your strategy to change things (whatever course you decide). Medically, you won't be affected for some time to come; don't fuck up your career/lifestyle/future by acting hastily. Fuck OSHA and any ideas you may have about crusading against your employer. If you have time for that after you've "made yourself whole", then fine, crusade--but take care of your life first.
4) As I said before, monitor your medical condition annually, or every 6 months if you stay "in the industry". Why every six months? Because constant monitoring leads to early help, and secondly, "3" years is a LOONG time technologically, and tests become more thorough and investigative as the technology advances. The "end" is not near; at least, not because of fiberglass. It may come sooner and be more debilitating than good healthy pink lungs would dictate, but we don't even know that until your test results are interpreted.
Step back; breathe. Take some time to think everything out. There's PLENTY of time to make the right moves later. Immediately change your work conditions, but all else can wait until you're not thinking "in shock".
