Hi everyone, it's my first time posting here. So here goes, I'm a 15y/o dude, abt a year ago I started having acne which I've got under control now, but it left red marks on my cheeks. Under yellow lights they aren't rlly visible but man, I look terrible under white lights and in the day! I mean, concealer does the trick, but I can't use them everyday right? It's srsly ruining my life... Whenever Im on tv or utube, all i see is clear skin! It's the holidays, but I find myself avoiding hanging out with my friends! I can't even look them str8 in the eyes... I've been using hydrocortisone and tretinoin cremas but I've yet to see any improvements. And my dermatologist said I'm too young for lasers, she told me to be patient, but I've been waiting for 6 months, I can't take it anymore!! I've tried lemon juice, drank way too much water and tea, so I'm kinda desperate now. I'm going to college the year after, I really can't bear to think what's going to happen if my red marks don't improve! 
( Does anyone have any advice??
You're so lucky that all you have is scarring, not like the majority of us still hanging round these forums trying to find something to get our skin on a leash 5 years counting...
Anywho, how long have you been using tretinion for, what strength is it? To get good results with that stuff you have to be as consistent as possible.
One thing I have discovered recently is something called a derma roller, the reviews i've read sound pretty promising, but you'll have to check it out yourself.
Here's one company that seems pretty reputable on the net or else maybe ask your derm. http://banishacnescars.com/
Keep in mind that hyper pigmentation will naturally fade by itself over time, again, you are lucky that that most of your problems are red marks and not pitted scars. 
Now its just a matter of waiting it out