Frequent Stomach ache in Child?

My seven-year old daughter has been complaining of stomachaches, 1-2 per week for the last month. Never vomits or has diarrhea, just has a stomachache. She goes to day camp and has problems with some of the other kids there and the counselors, she says the some of the kids make fun of her and the counselors are not nice. She goes there Monday through Wednesday and last week I had to leave work early due to her complaining of a stomach ache and also have to leave early today due to the same thing. When she is home, she says her stomach feels better and she acts pretty much normal. I am thinking there is something psychological going on here, but I don't want to ignore any possible physical symptoms. Any advice on this?