I went to the doctor for severe lower abdominal pain, all that he told me was there is blood in my uterus. is that just a fancy way of saying, period?

No: You can have a backup of clotted blood into the uterus called hematometra, which can be identified with a pelvic exam or a transvaginal ultrasound. Please consult your GYN for further evaluation and treatment.

See below: It could be. However, there are other reasons for having blood in the uterus. Do you usually have severe abdominal cramps with your periods? (if so, BC pills to cycle them can help). Might you be pregnant (and possibly having a miscarriage)? Call the doctor and ask his explanation first. If he/shje is stymied, ask for a referral to a gynecologist.