I am on buspirone for anxiety is it possible that that's the reason for my stomach pain and nausea? doctor says it's all in my head

Side effects: The pharmacy should've given you a list of possible side effects. GI upset is definitely one of them. However, don't be afraid to discuss this with your doctor a bit further by explaining other facets of what you're feeling that clearly make it more likely a side effect than not. Also, try taking the pills with a little food and see if that helps.