I came on my period as normal but it was extremely heavy and lasted from 23rd-4th I then came on again the same month on the 11th-23rd which was also really heavy and again on the 1st which lasted around 9days. I have been getting a lot of stabbing like pains and it is very painful during intercourse. I have told my doctor but he just said its nothing to worry about and put me on the pill. My mom had cervical cancer when she was pregnant with me and I'm scared that's what it could be. I am 21.

Your eating problem may have to do with this problem BUT maybe you should get a smear test done.

You need to go to a different doctor, get a second opinion. I don't think the eating problem has much to do with this, but the period frequency and the pain is obvious cause for concern.