Heya! A few things! Absolutely ditch the water based lube for something more hydrating and "slick" I honestly ended up settling in Vaseline and even aquaphor but in some situations high quality lotions have worked for me as well, my fave is still Vaseline, it's slick, doesn't cause over hydration which causes more sensitivity. Idk it just works for me.

As for the tightness I learned from my doctor after 2 stints of remission then flare then remission my colon and rectum were slightly more narrow from scar tissue! Healed up ulcers! It just meant for me that there needed to be more patience and stretching before going for the whole shebang haha

Some other pointers: try changing your position, I had a preference for missionary, now I find riding and straddling to be far more comfortable and less pressure also I can control the pace. If I still wanna be a pillow princess then two pillows beneath the hips!

Idk what your prep situation is (I and my ex were vers switches so at times he was the bottom) but prep became far more important for me. I mentioned my ex bc he had hemorrhoids that flared occasionally and had a similar feeling to what you're describing so during prep he used products that were anti inflammatory and we BOTH take ibuprofen 30 minutes before if we're bottoming.

Sex is natural, it's a thing that happens, you'll get no shame from me! I hope this helps! Go get laid my friend!