Too many possibilities, you need to see your doctor and get it checked out. Anything stressfull happen lately? Have you considered the possibility of it being GERD?
In any event only an EKG, CX and labs can rule out MI ... yes it's happened before at age 22, so see a doctor even if you think it's something mild.
Since you gave more info the only thing I can tell you is that you need an EKG read by an experienced MD. THere are a number of arrythmias that could cause you to have these sensations, some obvious and some not so. WPW
for example is rare but something that could be associated with your symptoms. No one here is qualified to make that dx so the sooner you see someone the better off you will be.