As Risingsun said, exchange it. It's a hard ring to fit, with 3 rings and twisting, you need some extra room, just not too much. Spend some time in the store walking around with the ring on, to see how it feels...
I agree with RS and Kaleigh. When I ordered a trinity ring from Cartier (which I canceled) I ordered it a quarter size smaller than my true ring size because they seemed to run a little big. They'll exchange it for you without a problem.
Thanks for the advice guys! They ordered in a smaller size for me and told me to keep my current one until it comes in. I don't swell too much during pregnancy, but I'm 7 mo. pregnant and I live in Arizona, where the summer temps are well into the triple digits. I have a feeling I'll be wishing I had gone smaller once this baby comes Wish me luck!!