I totally understand how you feel. This weekend, I was actually starting to glimpse the possibility of ab definition for the first time in a long time. So exciting. Then this morning, I was as bloated as could be, with a nice round belly. Thank goodness I KNEW what it was from, a combo of PMS and lasagne for dinner.
Don't stress too much over water weight, it will dissipate over time.
One caveat- if you are experiencing noticeable edema, where you are swelling up all over, and it's staying or getting worse no matter how you eat or what you do, please see a doctor, as swelling of that type can indicate serious health issues.