Chest tightness&heavy feelings...please help?

so I traveled three days ago from VA to VT two hour plane ride followed by two hour car ride. had breaks in between. ever since I've gotten home I've had this heavy tight feelingin my chest. it comes and goes and its mostly there when I'm thinking about it. I've had this before several times. had lots of ekgs and chest xrays and its all been normal. just anxiety. but I'm freaking out once again, like I said I've been traveling and stressed. so is this just anxiety? please help. oh and I'm 22 today it was gone for most of the day, and i was stressed out about being bored, and it came back. And now its kind of racing heart feeling. and anxious feeling. Also kind of painful. Ive taken asprin everyday, and I also worked out last night and was fine. I have a phobia of blood clots. Could i have a clot in my lung? or something... I over worry. Ive had tons of ekgs and chest xrays and its always normal.