I’ve never felt my strings

So I recently got my IUD and I have never been able to feel my strings. I’ve recently been having sex with my boyfriend because he came home from the Marines. I have been bleeding for a couple days and sex has been a little bit painful. I don’t know if it dislodged because I can’t feel my strings. He also was finishing inside of me, but I’ve made him stop just in case. Should I maybe buy Plan B, or am I just paranoid? Sorry this is my first IUD, and I’m just a little curious!?