Im 14 and pretty athletic. LATELY when I do a workout or get nervous I either puke/ feel like I will

First of all, you should check with your doctor, just in case. Also, if you exercise, you should also have a balanced diet so eat well. If you feel like puking or actually puke when you get nervous, at times it can be quite normal due to the nerves in your stomach but again, you should ask your doctor just to be on the safe side.