Ok im 19.. 145 pounds 5'10.. skinny little guy... and I wanna start working out and I got my routine (sorta) planned out.. im gonna be working out 3-4 times a week.. most likely 3.. and how long do u think the average time in weeks/months would it take to notice a difference? workout for about 45 minutes each time cuz i dont get much time (before I start my classes)