After Sex With My Husband My Stomach Swells Up And

After sex with my husband my stomach swells up and become firm and looks like I'm 4 months pregnant and I also get cramps with it.. I can't push my stomach out that far even if I wanted to.. This problem has just recently started.. I have fallopian rings for the last 10 years so that I can't get pregnant,if you could answer this would relieve a lot of stress for me