I think its normal to have some tightenings after sex and some pressure as well but i dont think its meant to hurt. If youre ok now i probably wouldnt call but if youre worried about it just call for reassurance. :) they are used to questions like this and itll put your mind at ease. The sperm does have a chemical in it that helps soften the cervix and if you orgasmed it also releases oxytocin that is i think the same chemical released during labor or to set off labor or something. Im also still active with partner and do get cramps and pressure but no pain. :)
Orgasms can cause cramping and sometimes contractions. You're probably fine but if you really aren't sure call you doctor :)
Sounds like what happens after orgasm. Of the cramping and pressure is gone the that's a good sign. How is baby moving? Like normal a lot or less?