Abdominal pain?

I am 14 weeks pregnant and really havent had cramps at all (though I know thats not uncommon in the first trimester). My stomach has been hurting mostly low in my abdomen, and its pretty dull but noticeable. I have been very constipated the past two weeks so I cant tell if its something to worry about or constipation. How long should I wait or what should I look for when deciding to go to the doctor. Additionally my abs have been quite sore for a few weeks. They just feel like they need stretched but I think this is from my growing belly. Any advice?