You might have irritated your urethra (pee hole) during sex, I'm 36 weeks and I get those same pains, you might have caused your bladder to contract, but it goes away in about 24 hours or so after drinking a lot of fluids.
I also have been feeling the pressure in my butt region when I have to poo so I think maybe you have a mix of things happening which can in turn, all trigger labor lol. Good luck to you! ♡ :) I deff think labor is near. Just keep on doing what your doing you'll progress. :) just make sure you stay hydrated!
Could be either...if it becomes more intense and closer together then it's the real thing. Same thing happens to me after sex with my hubby right now...mine always stop though.