i have had an upset stomach off and on starting at the end of the second trimester. i know you read everywhere that constipation is more likely to cause you problems but i also work with a lady that is 4 weeks behind me (im 35 weeks) and she has had days like me where you cant leave your house without fear of not making it to a bathroom! BUT, my sisterinlaw went into to early labor with my nephew and the first 'symptom' she had wasnt contractions...she had diahrea for two days first. either way, if it gets worse or doesnt let up after a couple of days absolutley call your doctors office. good luck and congrats!