Why Does it Still Hurt?!

So my BF and I have tried several times to have sex but it never really happened because it hurt too much. (I have a narrow vagina according to my GYN)
The other night we had sex and after a while, and me biting my pillow in pain trying to just deal with it, it finally went all the way in and it didn't hurt anymore and felt normal. 
However, we went to have sex last night (used lube, I was wet, whatever) and it hurt again so much that we had to stop and I couldn't do it. I don't get why, when I got a PAP Smear, I barely felt the Speculum and it wasn't painful, just uncomfortable. But when I have sex, I feel like everything is being ripped. I don't even really bleed that much during sex either...
What's wrong?!