Firstly, you're young. It's common to weigh less then. I ride with 6' folks who weigh 145 when they're in top shape and they're muscular, just not big muscles. They are also very fast! So I wouldn't worry about your weight or the size of your muscles or any of that. Sex partners care a lot less about that than many young people think. Fat is OTOH another issue. I don't recommend fat. I recommend focusing on having fun with athletic endeavors, whatever they are. Your time will be a bit more limited in university, but not so much that you can't get in an hour a day. I don't think there's any reason not to work out almost every day. Split it up between cycling and strength however it feels good. I wouldn't abandon one for the other. A mix works best with at least 2 strength workouts per week.

You have to eat protein to gain muscle. A little protein both before and after a workout is helpful.