C.O.
S.,
I can tell you are a very caring, loving, and devoted mother. I'm afraid that what I want to say will come across as harsh, so please know I mean well and am wording it the best I know how. While I don't have a teenager, my personal experiences as one are still painfully fresh in my mind.
To start, it's a very good thing that he apologized and asked for help. That means the hormones haven't completely taken over (ha ha). Also, I commend you on keeping your cool. That is impressive.
One of my biggest pet peeves about my parents as a teenager, and even now as an adult, is their nagging. While it is done with the very best of intentions, it only cultivates contention. To the person who is being nagged, it comes across as being condescending and manipulating. As a teenager, to feel belittled and controlled is the worst.
At 14, self-esteem is pretty much at it's lowest point. Acne magnifies that 1000%. Your son is probably feeling very much out of control and doesn't know how to deal with the anger and frustration that come with being a teenager, as it is more of a physical issue than anything else. Hormones do crazy things!
I recommend you give him his space. Yes, his skin will break out terribly if he doesn't use his medication, but it's his skin. When it bothers him enough, he'll do it.
In the mean time, let him take the reins and make his own choices whenever possible. I'm not saying let him do whatever he wants, but be respectful and choose your battles carefully while encouraging him to be the best person he can be. If it doesn't matter in the grand scheme of things, let it go. You don't want to damage your relationship with him over minor annoyances when he needs your love, support, and encouragement.
If your son is showing signs of depression or continues to have problems understanding and controlling his anger, it may help to have him talk to a therapist or even his school counselor. My mom made me see my counselor and, while I was embarrassed and ended up bawling my eyes out, it felt good to get a lot of things off my chest and he was able to give my mom an idea of what I needed.
Good luck! It's hard being a teenager; I can't imagine what it's like being the parent of one! I don't envy your position but I do wish you and your son the very best.