Gynecomastia (moobs) but i'm fit?

I've had gyno for about 5 years now, I'm embarrassed to be shirtless. I'm 15 at the moment turning 16 this year. I've become really fit and strong in attempt to get rid of this problem, and admittedly it has lessened but i'd say it's still a category 1/4 problem.

I'm fed up with it, honestly, i'm gonna be having sexual relations within the next 3 years and i cant seem to get rid of my gyno. I dont want surgery.

Is there any idea about the following:

What causes it?

What can I eat to lessen it?

What exercises can i do?

What can i use to lessen it (eg, cream or drugs)?

Is this permanent?

Thanks.