why am i feeling so nauseated during and after sex??? its getting worse...?

[M i S S Y.]

okay so me and my boyfriend have been having sex a lot lately. we dont use protection, he uses the "pull out method' [[no need to lecture, him and i both are fully aware of the consequences and are prepared if anything happens]] anyways, we had sex especially during the time that i was supposed to be ovulating. i noticed a couple days ago after we had sex that i had been spotting during sex. i thought it was my period, but it turned out i was just spotting. and lately every so often ive been getting nauseaeted after sex, not really nauseated but enough for it to bother me. but lately, the past couple days especially today i was getting really nauseated after we had sex to the point i had to go to the toilet just in case i threw up because thats what it felt like. and a few hours ago i was actually feeling nauseated DURING sex and i felt like i was going to throw up and after i went to the toilet real fast and acutally did throw up.
i read somewhere online that when your having sex and a guy hits your cervix it can cause you to be nauseated....but is it supposed to be this bad??
what could this be...?
Im supposed to start my period tomorrow by the way//
help please