I'm sorry to all those with teens suffering 
I was a teen who was prescribed anti-depressants at a very young age, initially for disordered eating, followed by depression and self harm and then in later teens/early 20's anxiety.
I think anything above around 16-17 is an OK age to be taking AD's, but should largely be looked at on a case-by-case basis (i.e; look at pro's and con's, can teen benefit from speaking therapy beforehand, how severe is the MH). I was put on them at 14, which is insanely young and the medication I was put on was advised never to be given under the age of 16/18. There are however AD's which are less severe in nature (think SSRI's - citalopram, fluxoetine) which I believe are now routinely used with the medicating of anxiety and depression. My experience started in the 90's where I've been told that the use of AD's before adulthood was less common, but I'm not sure how much truth there is in that.
So, with that in mind, I believe medication can and should be used - your son OP sounds like he has a pervasive pattern of anxious thoughts that then manifest into physical symptoms - you said the psych said he's "very self aware" but in my experience, when untreated, being self aware is usually very difficult for those who are suffer from anxiety/depression - because naturally, you focus on yourself and how you feel, which equals stronger reactions/emotions.
It's good to hear he's with a psychologist, but oftentimes "talking" isn't really enough, those with anxiety need practical tools that enable them to tackle the anxiety. If the anxiety is very pronounced (which it is at the moment, leading to "hangovers" - this is v common btw) engaged in CBT will be possibly too overwhelming and counterproductive in some regards as your DS will be "rehashing" the reasons as to why he feels anxious. The CBT would be best left for the time being, until the physical symptoms are managed, then reintroduced phase by phase. Sometimes backsteps will be taken but they are VITAL because thumbing something through can end up with further distortion of thinking, or hopelessness toward therapy. I experienced both, which put me off therapy for a very long time - had someone said to me "It's OK not find it working" I believe my MH journey would have been far shorter.
I wonder whether your DS panics about the physical symptoms themselves? I know I used to panic about panicking, however perverse that sounded - and in the midst of a chronic 4 months I would quite literally hole myself up in my room for fear of panicking in public. I was 22 and wouldn't leave the house without somebody with me who I trusted (which was at the time limited to Mum and my brother). What really helped me was to know that you can't die from a panic attack - once I understood the physical process of a panic attack, I could better control one - I knew that gasping for air made me dizzy and sick, and that I was gasping because I was hyperventilating and feeling I couldn't breathe, but the very fact I felt dizzy and sick was because I was taking in too much oxygen, and that if I slowed my breathing down, all the symptoms that were scaring me would disappear because rather than being suffocated through NO oxygen, I was actually flooding my body full of it. I don't know why, but ever since I read that bit of information, my attacks are seldom and very brief in nature, linked only to when I feel sick (I have emetophobia, although it's a lot better than it has been and was my anxiety "trigger).
Lastly - can I tell you that I can almost 99% promise that if you are afraid you're not doing enough as parents, or that you are wondering if you're doing the right thing - you're doing BRILLIANTLY and believe me, your kids will be so grateful for the kindness, support and love you've given them. My Mum was my rock, still is - I do still call her when I panic sometimes (I'm 31 and pregnant!) because we all have moments when we need our parents. The doubt you have towards whether you're doing the right thing is entirely normal because you love your children and want what is best for them. I can tell you as a teen who had many, many years of MH issues (mine escalated for reasons beyond anxiety/depression), you Mum's are the reason we keep going 