Ok, then that rules out a potential cause. I get all jacked up hormonally from breastfeeding and that affects my libido and my ability to umm, self lube, if you know what I mean.
So you might have a hormone imbalance caused by pregnancy. Because pregnancy changes your body in so many ways, all kinds of things get messed up. The best thing you could do is go to your OBGYN and say, this is what is wrong and I'd like to have my hormone levels checked. It may be the cause of your problem. You might want to find a female GYN. I've noticed they tend to be more willing to listen about stuff like this.
It could also just be the typical stresses of having a new baby. Whatever it is, as far as I can tell from everyone I know and everything I read, it is TOTALLY normal and really common. I sometimes wonder if our bodies instinctively shy away from intercourse again so soon after having babies to prevent us from having another one so quickly after. If that makes sense.
Hang in there! I know how rough it can be, but we are here for you!