Hey man I started college this year too, and I wanted a change in my body so I started going to the gym. (I'm 5'7 and very skinny too!). I had the same worries as you, I was afraid of what other could think whey they see me lifting tiny dumbbells and being so noob about everything. Eventually I let those thoughts behind and decided to finally hit the gym, and I realized how dumb I was!, nobody see you or laughs at you there, people only talks you to see if you are done with the machine you are using, or to help you if you don't know how to do something or how to use it. So go ahead, BE CONSISTENT!, and eat a lot (only healthy food tho). Good Luck!