I need to gain weight...how?

im 17, 160, 5'9''. its hard for me to gain weight. i eat everything in sight. i got really serious with workin out 2 years ago. i bench 260, squat 405, clean 220. if i were u i would laod up on calories. go to a GNC they sell weight gainers there that hav 2200 calories per serving. they last a couple of weeks and there like $40-50 so if u want to spend that much, but youll gain weight. also take whey protein and mix it with a teaspoon of creatine within 30 min before/after ur workouts. youll see results after a week trust me. u got a gym memorship, if not then get one and go at least 4 times a week.