IUD, now painful sex?

I have been with my boyfriend for about 3 months and I got the paragard copper IUD a few weeks back.  Previously, we had been using Skyn condoms because I am allergic to all the other ones.  Now that we aren't using condoms, if we have sex too many times in a row, I feel a very sharp pain in my vagina.  This never happened to me before with the condoms. Any ideas?  We are both clean of STIs.  I have an IUD follow up in a week or two, so I will bring it up then, as well.