Cramps day after sex?

My boyfriend and I had sex lastnight , and I am currently feeling slight discomfort in my lower abdomen. He is on the bigger side so he does go pretty deep causing slight pain at first but it doesn’t last long. We used condoms and I’m on the pill so I’m not really worried about anything pregnancy related, but my question is has anyone else experienced this or know what the issue may be? Is it just because he’s bigger?