I agree that you want to gain strength. When I was 22 I started boxing and at the same time tried desperately to gain weight as I was 5'8" and 130 lbs. I boxed at 132lbs and made it to #1 in my province, continuing to box for about 6 years as an amateur. Later on it became more difficult to keep the weight down so just focus on that strength and the weight will slowly build.

Best of luck to you in your quest but don't worry too much about the 150 lbs and enjoy the lower weight because trust me it won't last!!!

cheers, fraser