Cumming Problems. HELP!

Cece
So I have been having sex with a guy for awhile and the first time we got a hotel together and he is not my first. We went through the motions of foreplay and I ended up cumming for the first time and only time ever with a person. 
Now when we do anything, it's almost like this pain in my lower stomach. Like a pinch. But I don't even remember the first time and what I did to make myself be able to do that? It almost feels like I have to pee and I have a hard time relaxing. 
Are there any tips to relaxing or getting in the zone even when I'm really horny? 
Thank you!