Girl, i had an impacted bowel they had to take care of as I was going into active labor for my first...o_O My dr had recommended enemas, colace, fiber, lots of fruit. Basically downplayed it so that I felt like I was blowing it out of proportion, although I don't feel I do that normally. In any case, none of that crap (pun intended) worked for me. Coffee didn't either (although to be fair, i couldn't really drink it due to a preg aversion).
ANYWAYS, for my first two pregnancies, i was constipated...I think I over-pee, if that makes sense. I use Miralax as needed, and my second pregnancy went off without a hitch. You don't have to use the full dose, nor may not have to do it every day. I play it by ear.
Good luck. Being constipated is no fun.