Do I have asthma to exercise?

So I'm 14 and 5'1"and about 15 pounds overweight. I also have a bit more muscle than you average teen. Whenever I start a run I feel fine then during my run I have shortness of breath, followed by a tight chest. When I have a bad tight chest I feel panicked that I won't be able to breathe I have a feeling like my airway is closing. I also have a dry mouth which is weird because simultaneously I feel like a have too much liquid in my mouth. Either saliva or mucas I dont know. I feel like I have to spit. And I absolutely know that my heart is going way too fast. I know this might be because I am overweight but I think that's only a little part if the problem. Help!! ~Can't Breathe