I am due with my sixth child September 13th and have the same problem. One thing I did do was have my thyroid checked and found out I have hypothyroidism. Also, keep up the swimming, walk a lot. Do you belong to a gym? It would be good to talk to a staff member of the gym, if you do belong, and see what they recommend. Ask health professionals, sometimes they know. Also search the web, there could bevaluable informaiton on exercises on the web. I wish I could tell you more, but I am in the same boat and trying to eat right (less fat, cal, hydrogenated oils and such), but the recommended caloric intake is supposed to be 2100-2400 calories a day. A lot, huh? So, I feel your pain.
If you need a friend, email me at ____@____.com. I live in Antelope, north of Sacramento.