Hi. I Had Menstruation For 8 Days (most Days Heavy)

Hi. I had menstruation for 8 days (most days heavy) last August then 2 period cycles in September (13-17) and (25-28) and then I got my period again starting Oct 5 (I'm on my 3rd day today) and its still pretty heavy. I am worried with what this could be. I am a 27-year old woman weighing 84lbs. I am a full time student doing my masters degree with a part-time job. I am pretty much happy with my life (except this) and eat mostly healthy food (mostly home cooked) since my boyfriend hates to eat food from fast-food shops. What do you think causes this and what can I do to have a normal (regular) period? thank you so much for your help