I'm 16 and I have a quite a large raised lump that varies in height above my penis on the left side. It is hardish but when I press it it goes down and it feels like there could be a gland or something inside. I can't really remember when I discovered it but I don't think it was that long ago, but it eventually comes back again but not after a specific time. Any ideas what it could be because I'm a bit embarrassed to ask anyone about it or go to the doctors.

It's probably a gland. There's nothing to be ashamed of anyway. Go see a doctor, show him the lump. Doctors have bodies, and some have penises. If it is something serious, it's better to find out sooner than later.