The following is likely to make you even more crazy than you are now. Sorry.
You're leveling the reticle. Another, arguably better, approach is to level the erector assembly. It's not safe to assume that the reticle is installed with the vertical axis perfectly parallel to the direction of travel of the erector. I had a Leupy for a while, and the reticle was a full 5 ° off from the erector. Called them, they said it was within spec.
If you dial for elevation, you should probably level the erector assembly. If you're holding, level the reticle. On most good quality scopes I've tested the reticle lines up nicely with the erector, but not always.
I regularly have the experience of going to the range with a scope I know is perfectly level and having it appear like it isn't. Even a slight slope at the range can totally fool your eye. To convince myself I wasn't crazy, I took a 6' level to the range one day and set it out at 100y. Shimmed it up perfectly level. Looked at it from the shooting position and it confirmed all was well and the ground was just confusing my eyeballs.