My chest and upper throat is tight I had a blood clot but now gone but I still have trouble breathing. My doctor says my heart and lung are healthy?

2nd opinion. This is a problem that requires a face-to-face meeting with your doctor. In that meeting, your doctor will listen to you, perform a throrough examination and possibly order labs or other tests. Based on this information, he/she will be able to tell you what's wrong and what to do about it.