This is definitely not a disorder, actually it's quite normal for your age. It seems that you are experiencing sexual arousal in the presence of men. It might point on you sexual orientation, but It also might be an outcome of confusion, which is very typical for young guys at your age.
Anyways, there's really nothing to worry about.I do suggest that you have a conversation about what's bothering you, with a grown up you trust, and feel comfortable with.