Your belly tightening up are contactions and the vomiting is probably from baby pushing on your stomach because he or she may be running short on room in there (Assuming you're nearing the end of pregnancy) not sure about diarrhea. If it's bad I would definatly consult your doctor. Dehydration is not good in pregnancy and can actually be the cause of contractions.
the 13th lucky. im quite the 24th
Omg im goin threw the same thing. But im 36 weeks im jus ready for it to be over with come on may 13!!
No that happened to me when my body was ready to go in labor.. its normal tell ur doctor