Abdominable pain and tailbone???? Whay is this????

Hi I'm 17. I have been having this really bad pain in my lower abdomin and around my lower back (tailbone area). I have been having massive weight gain over the last 7 months. I have had reall bad swelling in my feet and ankles. When I walk and now they swell even when I am laying down. Like when I wake up in the morning my feet are 5 times bogger than normal size and they are numb and throbbing when I stand up,almost like they feel asleep. I have been having some chest pains and massive headaches if my lfet leg starts swelling. What could this be. I knw for sure I AM NOT PREGNANT. That has already been ruled out. So please if you have an answer. My grandmother passed away 3 months ago from having severe hymocromotsis and my doc says I dont have that. I dont have any health problems other than this. I had my appendix taken out nov. 08 and my gallbladder taken out jan 2010!!! Other than that I had a son in Feb 09 and it went very well. Except I had seizures for 2 months after he was born but that was an allergic reaction to epidural. So please anyone any reasonable answers!!!!!!!!!!!!!!!!!!! :'(