What is most likely to be wrong with me?

I used to be a very healthy person, mental, and physical, until December of 2010 close to new year's eve, I started to have a bad panic attack and yet I do sometimes from time to time, but things since then has just gone downhills.
I thought I could handle it until, later on, I started to have vertigo and balance disorder, and then I had an MRI taken and nothing was there more than sinuses infection, but I took medicine for it, so it supposed to be gone by now, and yet I still experience the falling down feeling, and also, stuffy head where even my eyes feel heavy.
I had couple electrocardiograms, and I was discovered that I didn't have any heart problems, had blood tests done and nothing, well, now, lately, I started to get chest pains and back pains, and burping for 2 weeks so far, and last night I had this very horrible pain on my uterus because of gas problems, and also I went to the gynecologist, gave me a pelvic exam and said I was fine.
I tried to convince myself and relax saying what my parents tell me "It's in your head" but then whatever is in my head, it feels like one of these days it will kill me....because it feels like life wants to destroy me from every side.