Is this pain coming from Endo?

First of all - this is about my partner, not myself. But we are at a point where we're broken.

My Wife has a feeling that she might ahve Endo for years now. But she never did surgery because, well first of all nobody really wants surgery at all if possible - and second her doctors say it's not necessary with her current symptoms.

She sometimes has a slightly swollen belly and pain in around her uterus area but nothing unmanagable.

But for 5 years now she also has regularly UTI symptoms and problems. We tried anything possible, from teas, D-Mannose, different underwear, different detergent for the washmachine and and and.. i couldn't list it all really.

But the Problem also is, this UTI symptom mostly only comes a day or two after sex.

Now we also tried many different things there to make absolutely sure there is no bacteria involved in any way. And while she has those symptoms (burning and pain - often needs to pee) when she gets tested at the Doc, there is no bacteria found.

I also got tested, with negative results.

We have no more ideas what we can do against it. Could this be Endometriosis? Before or during sex, there is no pain - maybe only for a few seconds in the beginning, but not during it.

But is there any relation to endo? Could the friction cause this UTI symptom even if no bacteria is found? And if it's Endo, is there anyway to prevent this or reduce the pain?

We have no more idea at this point..

After years now she got antibiotics from her Doctor. While im against using them when there is no bacteria found (she doesn't get tested anymore, since they never find anything) she says it helps her and the day after she feels better.