Hi Lachomba,
Unfortunately, there is probably no private insurance company that will cover your "pre-existing" conditions. Unfortunately, we do not have a "healthcare" system in the U.S. We have insurance. By definition, healthcare is for people who are already in need of it. Insurance is for healthy people who have not yet shown symptoms of a problem.
In the insurance companies' defense, (or any company for that matter) I can't imagine why they would take a couple of hundred dollars from you knowing they are going to have to spend a few thousand on you. That's just bad business.
However, you still need insurance for two very solid reasons!
#1 is even if it doesn't cover your menstrual cramps, it may cover things that haven't developed yet if you qualify for it. Injury from accidents, cancer, heart attack etc. are all very real situations. And if you think a $900 hospital bill is a lot, wait until you see a hospital bill for one of those problems (hundreds of thousands). And while the law says they must give you treatment with or without insurance, the reality is you won't receive the best treatment without insurance. That's because hospitals and doctors are also in business and must focus on the patients who will pay them if they're to continue in business. It's a viscous cycle.
#2 is that while insurance may not pay for your menstrual issues, you may receive enough of a discount by being a member of the insurance companies' network. After all, the insurance companies don't pay what you pay, they pay less through pre-negotiated rates. By having their insurance, you'll get their pre-negotiated rates also. That may pay for itself and then some.
I hope I've helped.