What do I do?..

About an hour ago I had sex with my boyfriend. I was riding him and he was like moving my hips and down and he brought them up so when he tried to bring me up off him I thought he was just.. ya know. pushing my hips up bc that’s what we’d been doing. and I try to go down and he makes this face and pushes my hips up and off his dick and i’m like... *bf name*... and he just made this face and I was like *bf name* and he said baby I just came. I said were you out(pulled out)? he said “mostly..” and now I have cramps like period cramps but my period doesn’t come in a week and a half and i’m thinking it’s just like after sex cramps but that doesn’t usually happen for me, I don’t think... but it happened Wednesday night too and my stomach doesn’t usually hurt like that after sex. What do I do? Any advice, tips, or explaining what could be the cause of any of this?