Cramp & Nausea During Intercourse

So me and my boyfriend have been having unprotected sex consistently for about some weeks now and he always finishes inside of me. I never think anything of it being that i am on the Nexplanon implant. The past few days i've been experiencing a really bad cramp during intercourse and found myself sitting in front of the toilet spitting as if i were about to throw up, I know i may not be pregnant but what could possibly be going on ? This has never happened before 😨