vaginapagina | Instead Softcups and Sex

I've been using the soft/instead cups for a few months now and I love them but I wondered if any one if familiar with scrapping or injury stemming from wearing them during sex?

On occasion if I use them I will feel an odd cramping after, painful and sharp, disassociated from any period pains (which if we're sexually active are usually non-existent anyway) though this seems rare. I'd had a number of health issues for a few weeks and it seems like they started when I first used the cup and we'd had sex with it in - which I've only remembered now in hindsight. For about three months I'd taken more antibiotics than I'd taken in a lifetime but I never related it to the cup or injury because during the act, neither he nor I can feel any contact, shifting or pain. And if he can feel it, he has never made mention except to say so after because he feels a bit scratched.

After 3 months of doctor visits and persistent UTI's (or something that presented as a UTI but wasn't high WBC count but no infection present) my (new) GYN said sometimes couples just don't mix well in terms of physiology so she gave me a mild antibiotic* and told me to take it when and if I thought I needed it. It seemed to work and our sex life was back to normal in a flash, but since then we've tried again and now I'm feeling a bit... off. I've taken the prescription but I wonder... is this an injury my body seems to be healing from? Has anyone else made any mention of injury while wearing the cup during sex/any of the pain problems it's caused? In my pre-purchasing research I'd just heard that this was a wonderful perk, but hadn't seen any complaints. Or can the cup cause UTI's? I don't see why it would...

*the scrip she gave me was a low-dose Macrodantin, I am on the pill and she knows we're not trying to get pregnant. Should I be worrying about the drug interactions when/if I take this medication? Is it known to lessen the effectivity of the pill?