How to Strenghten My Punches

I'm currently boxing for a college team right now. I'm still a beginner, only a month into it, although I am learning a lot after than many of the other beginners. I'm 19, turning 20 soon; I weight 140 lbs, but plan on dropping down to 125. I want to eventually turn pro after a few years.
Anyways, I've been hitting the mitts and the bag for a while now and my punches aren't necessarly too weak, but they aren't strong by any means. My brother, who's only done boxing for fun for about 2 weeks has a really strong punch. We were comparing how hard we hit the heavy bag and it seems his punches are twice as strong as mine. I'm punching correctly, using my hips and legs, but its still seems somewhat weak. I was wondering what kind of training/workouts I could do to get stronger punches. Also, is there anyway to get used to getting hit if I'm not allowed to spar in the gym yet? (random question)

maybe you dont have enough snap in your punches,but if you hit the bag 3-5 days a week for years you cant help but to punch harder eventually...as of now your an amature so you dont need to worry about hitting hard really,trinidad only had 12 KOs in like over 100 amature fights ,also a strait right own the middle if thrown correct by anyone and lands on the chin will KO someone ...so practice on accuracy and KO power will come ;)

I've only stopped on lad so far, all my other wins are on points... I don't mean to brag but for a 81kg fighter I have one hell of a dig I hit as hard as a lot of people who have about 10kg on me.

The reason I haven't knocked loads of fighters out whilst competing is that most of the lads I have fought have been fairly tough because of their styles as well as the way Amatuers fight I haven't always been able to land shots with all my weight behind them.

Don't look for the hard shot and you'll land it. just focus on keeping your hands loose and fast and keeping your technique right, you will soon learn how to transfer that into getting a pop in your shot.

it's about range, technique and speed.

keep your arms loose, then snap, and tense your body at around the last 4 inches before you hit...
thats the basic explanation of how to punch hard but its better to be shown and to practice it... also if you just pick you punches right they goner hurt neway
peace