HELP ME PLEASEEEEEE

Alyssa

I have an iud placed and my boyfriend came over and visited me and we ya know had sex, before he came over I check my strings and they were in place. He came in me and I went to recheck the strings after he left and I can’t find them, should I take a plan b or not ?!?!? I don’t wanna be 16 and pregnant but idk if I’m over reacting