I've had two periods this month that were two weeks apart... the second one is heavy with a lot of clotting. is this something to be concerned about?

Possibly: Two periods is not common in the same month, especially with one being heavy with clots. I would call your GYN Dr and get an evaluation with them to assure all is stable. As you can never go wrong by getting a Physical exam and possibly even some testing such as a pelvic US if the issue persists. Best wishes.

Maybe yes, maybe no: If you are sexually active, the second period could have been an early miscarriage. If not, you may be just approaching perimenopause. The one think I would be concerned about would be the possibility of endometrial carcinoma. As such, let your gynecologist know. S/he can take lab tests for hormone levels, do a transvaginal ultrasound to look at your uterus & may want to talk about biopsy.

You could have: a hormonal imbalance with breakthrough bleeding. If this recurs - would d/w your gynecologist/ physician. Take care.