I mean, that would be considering there is no interest at all. Yes if you would put it under a mattress, sure. If you would put it in s&p for instance, even on the low end you’d be getting about 6%. At that interest compounded monthly, you’d be able to be a millionaire at about $1000 a month, or $12000 a year. Still a buttload, but not unfeasible for dual earners without children, depending on where you’re located and in what industry of course.
Well first of all, vaginas don’t stay the same shape the whole time. The more turned on a woman is (and relaxed) the wider it will be. It can be if she was particularly excited, because it was the first time, it was very wide open. It may very well feel different the next time.
Second of all, there is a possibility you have desensitised yourself due to death grip while masturbating.
Whatever you do, don’t put the blame on her/a singular body part of hers. If you want, you can try and see how you can make it work together, maybe it will be different next time, or you can try different positions. If that doesn’t work out, just tell her that you feel you’re sexually incompatible. Don’t mention her body parts, just be clear that you just don’t feel the sexual chemistry is there for you, and that that isn’t her fault. For someone else she might be just perfect, but for you it just isn’t the right fit (no pun intended).