the reason why they tell you not to lift weights is because it produces short tight muscles but what you need to boxing is long lean ones. 6'2" and 170 is a very good size. I Think if you wanna get bigger you need to eat more and do more of the exercises you say your doing it sounds like youre not diong nearly enough.

my regular day includes 3 miles is moring 20 40 yard sprints uphill. get to the gym about 5 pm run another 3 miles , 30min of jump rope, 30 min shadowboxing. 4 rounds of pads, 5 heavy bag, 5 double end, 5 uppercut bag, 400 pushups, 100 pull ups, lots of punches for cardio on heavy bag, never truly counted but well over 1,000 different kinds of crunches and sit ups. try not to lift weights every day i usually do them maybe twice a week