Someone help

Okay so I'm on the pill, and I take it regularly, there was I think maybe one day I forgot to take it in August and maybe one or two days in September. I didn't double up on the pill the following day after I forgot to take the pill (hopefully that makes sense). Last weekend, I did have intercourse and I'm sure I took it that day, but I'm still just worried. We did "doggy style" and afterwards my stomach has been feeling off - it doesn't hurt dramatically just kinda, idk really how to explain it other than it just feeling off. Idk if this is normal, but I suppose my stomach feeling weird is what is making me paranoid and worried.

If anyone could possibly reassure me and/or explain what is wrong with my stomach and if that's normal or not, I would appreciate it.