You are a young person! This is good as things like heart disease, hyper tension and diabetes are a little less likely. This breathlessness when excited can actually be a symptom of anxiety. You are not the only one that has this shortness of breath happen when excited and there are a whole host of reasons for why this might happen to people. Here's an article that is really a good read. https://my.clevelandclinic.org/health/articles/9446-positions-to-reduce-shortness-of-breath Here's another little slide show https://www.webmd.com/lung/qa/what-are-treatments-for-breathlessness-caused-by-anxiety
Would you say you are an anxious person?
im not sure it maybe diabetes or a problem in the blood pressure