Do you take it with food? I've also heard it's good to take it with dairy, so maybe a glass of milk or some cheese.
If you keep having trouble, maybe try a liquid calcium instead of pill form.
Highest known weight: 324
Weight on morning of DS surgery: 308.5
Got down to about 185 before pregnancy;
Benjamin David born March 24, 2012, 7 pounds 11 ounces