At 17 lift heavy freaking weights and eat a lot of food...not necessarily a lot of crap...but a lot of food.
Don't worry about body composition too much now, especially given your stats. If you were a complete fatass I'd tell you differently, but your not if your stats are right.
Shoot for 4000 cals a day and see if you can hit it...the bigger you get the more you will need.
You are at an age where some people build massive amounts of muscle and get somewhat leaner as well.
Growing is cool. lol
Between 17 and 18 I put on 25bls or so without a change in bodyfat.
Be dedicated and it doesn't happen overnight.
It takes time...years even.
Keep it up and train hard.
Don't worry about your friends, just yourself everybody's body and genetics are different.
Make progress yourself and you will be fine.
Something I always tell myself...there may be those that are better than me, or those with better genetics, but I'LL MAKE DAMN SURE NOBODY WORKS HARDER or wants it more than me. I am a former athlete turned bodybuilder and the athletic background has caused me to adapt that motto to most if not all aspects in my life.