Burning labia after sex??

Hey all! I need some help with this! Last month, I had a IUD inserted. I have lightly spotted ever since. But when my boyfriend and I have sex, I notice my inner labia kind of burns and stretches (it kinda feels like) when he inserts his penis. The sex is fine and he most of the time finishes inside me. After, I go pee (because I don't want a UTI) and it BURNS. Even after I wipe, I am still really sore. Has anyone ever experienced this? What can I do to stop the burning?

Thanks ladies! <3