I have chest pain after being on a trampoline for quite a while, it is uncomfortable to breathe.

Costochondritis: It's possible you have costochondritis, which is inflammation of the chest wall. This often occurs after straining or exercise. If the location of pain hurts more when you push on it, then this is almost certainly what it is. The treatment is rest & ibuprofen. If this doesn't help or your symptoms worsen (fast, difficult breathing, wheezing, increased pain), you should seek immediate attention