I notice the same thing sometimes but a little different. Sometimes I will feel a burning sensation so bad afterwards that I have to put a pillow between my legs and bite my tounge. The pain hurts even worse if I try to pee afterwards. Though it is also achy like you say. Besides the extra blood flow I believe it is also that we are more sensitive when pregnant. We need a little more help to get us in the mood. Which in turn gets the proper amount of lubrication. If DH or DP just jumps right in it is hard to get lubricated and it can rub like a rug burn afterwards. Have you noticed that you are not quite as into it when it hurts after? Maybe suggesting to DH or DP you need a little bit more. Sorry for the TMI. lol Hope this helped