Chest pain/stomach pain for five days, maybe heartburn?

I drank a tall glass lemonade five days days ago, and six hours after drinking it (and eating nothing in between), I started having a sharp, uncomfortable stomach ache which moved up into my chest, giving me heartburn I THINK ( not a burning feeling, like a really bad stabbing, pressure feeling) in the center of my chest. The last time I had a little lemonade a long time ago, I started getting the same pain in my chest but not nearly as bad, and I took a nexium which stopped the pain immediately.

I've had to sleep sitting up the past four nights because if I lie down for even a minute, the pain starts getting worse. I've had the pain non-stop for five days, varying in degrees of pain, from a dull ache to a sharp stab, and it seems to be unrelated to anything, eating doesn't make it worse or better, the pain just seems to have a mind of its own.

Also, the pain seems to take turns between my intestines, stomach, and chest, and I'm bloated due to constipaton. I took a nexium every day, and drank some antacid mix-in, tried a pepcid, tried tums, tried baking soda, tried vinegar, drank milk, ate bananas, but nothing's helping. What should I do? What could this be?

[xetoilenuitx]

I'm only 17 years old and at a healthy weight, my dad had pain like this but took nexium for a month and his heartburn stopped immediately. His heartburn wasn't a burning feeling either, more a stabbing pain, which he at first thought was a heart attack.

I started getting that pain maybe, three years ago, and I get the pain only a few times a year, but when I do, it's pretty bad. Sometimes I can find a cause for it, like spicy food, but sometimes it just seemed completely random. However, when I get it, I would take one of my dad's nexiums, which I know I shouldn't do without my own prescription, but it was literally the only thing that helped. Now it doesn't help at all and the pain has never lasted longer than a day and never non-stop pain, but now it's lasting five days, so far.

I've had some other symptoms too, like nausea, dizziness, lightheadedness, and headaches (but they may not be related). I've had pretty bad gas and have been burping a lot.

[xetoilenuitx]

And one more thing, I dealt with anorexia for the last three years, but I'm eating healthy now and at a healthy weight again. Could my low food intake have damaged my organs some how, and could this pain actually be my heart? Two years ago, in the midst of my anorexia, I was in class and started feeling a horrible pain in my abdomens, that moved up into my heart and caused me to faint from the pain. It happened really fast and there was no explanation for it, I hadn't eaten anything weird, I just had toast for breakfast, and it was my first period class.