I have three pea size hard round lumps around my right nipple. no swollen lymph nodes. i am a male in my twenties, i see a endocrinologist soon. i have terrible stomach issues too. can this be gynocomastia? tumors? or breast cancer?

Tumor just means "swelling." So three lumps on your breast are tumors whether harmful or not. You will have seen your primary care doctor - if not, please do! to discuss your lumps. You will want to go to your doctor(s) with a detailed and clear, dispassionate explanation of your stomach issues as well as any labs or tests that have already been done. Best wishes.