Feels like uterus cramping

[Zen]

I've never heard of passion cramps but if I ever had any I sure haven't had any lately.

The uterus can have muscular contractions, I would compare it to any other muscle with an imbalance of electrolytes causing cramping/contractions.

Only on a hill climb? It may be related to the muscles you're using at that time, i.e. you position on the bike.
My vote goes to the usual suspects, hydration and electrolytes. If you can find a flavor you like try mixing a 50%solution of gatorade instead of just water for those hot days.

Your doctor looks at you funny because 1)the insurance company allots her ten minutes with you and she doesn't really have time to think it through, and
2)she's probably not a cyclist.