Am i doing the right thing?

i am 15 1/2 and 6 feet tall. I weigh about 175 pounds. i have done online body fat tests and got results ranging from 12-15% depending on the site. over the past month i have stopped eating bad food and really took a whole new perspective from a dietary standpoint. i weighed anywhere from 180-183 a month ago and i find that this has helped however i want to take it to a whole new level. since ive been 14 give or take i have been hitting the gym off and on but im ready to really be commited at this point and i want to know if im doing the right thing. currently i am trying to shed the extra layer of fat that i have but its not much at all, maybe a pinch off my stomach but i want abs. i do a vigorous ab workout everytime i go into the gym(atleast 5-6 days a week) but my main concern is dealing with my cardio workout. i am doing a routine that consists of interval training. on a treadmill i am warming up by walking at around 3.5mph for 5 minutes and then i increase my speed to 8 mph for a minute and then back down to 5 mph for 2 minutes. i repeat the run/jog interval 3 times and then i cool down with a 5 minute walk again. am i doing the right thing?