Yes, I'm in my second year of university and I have felt like this throughout my A-Levels. Slowly easing into a routine usually works for me, attending every class and studying a few hours a day burns me out quickly. If you skip classes, you could start attending a few a week and gradually increasing. For revising, you could start doing 10-20 minutes a day and gradually increase to 20-30 minutes every day etc. I got D's, E's and occasionally U's in my Year 13 mocks and towards the end of Year 13 and did this method from a few weeks before and ended up revising for 9 hours a day without being tired a few days before the exams. I ended up getting C's. Since it's so early in the school year, I think it's possible for you to get A*'s, A's or B's if you do this method. Regarding feeling tired all of the time, I used to sleep 15 hours a day with still being tired when I was awake. I took blood tests which showed I had severe anaemia and minor hypothyroidism, prescriptions definitely helped me even though I doubted them. You could also take vitamin b and vitamin c tablets/dissolvables which you can usually buy in pharmacies like boots or beauty stores like superdrug. Sounds cliche but eating healthier also helped with my mood, motivation and energy. Regarding your skin, I also had issues with mine. Different things work for different skin types. I stopped using a skincare routine when my skin looked and felt damaged and only used micellar water and my skin cleared up in a week. Otherwise, make sure your products work well with your skin and you're consistent with it. (I also recommend acne patches as it usually works faster than witch hazel/acne gel). The app 'Skin Bliss' helped me with my skincare routine. Hope you feel better soon!