Your welcome 
Your situation sounds very similar to what I experienced more as a young child. Part of the abuse I suffered was violence towards me. Unfortunately this can bring us to a breaking point, it is something no human being should be exposed to. And when it gets too much the mind will find a way to escape in some....It seems that has been the case with us. When trauma has inflicted a chemical imbalance that will also effect memory in my experience. In my humble opinion I think it's a good thing not to remember or not try to as that's the minds way of protecting itself to heal.
I still sleep a lot from the breakdown I had which was about six years ago, but I have also had a lot of trauma since. So it depends on the personal circumstances as to what's doing what now. And medications can induce sleepiness. Have you discussed this all with your psychiatrist? As they can adjust medications if they are too strong or not working adequately etc. If it isn't the medications then this can be the body's way of healing - needing more sleep. Although frustrating it's not a bad thing if it does not interrupt your life to much. And in time you may find you need less as you get stronger - and you will.
Don't feel guilty if you can't study or take in as much as you would like to, it's important for healing to work,within your own personal limitations; doing your best is enough for now and all any of us can do. That's enough - your health and well being if the priority. The fact that you have not given up and still trying is a testimony of your strength. But I do understand how those mental symptoms can take its toll at times. Then it's living one day at a time - sometimes moment to moment.
In my own personal life experience recovering from a complete breakdown takes time to recover - and this time will depend on the individuals lifestyle, supports in place, treatment options and circumstances/stress they are under presently. Trauma recovery time is as Individual as the person - but it is definitely possible. I still have my relapses but have come so far from 6 years ago. And in time you will too. There is light at the end of the tunnel, never give up hope. Don't let it limit belief in what you can achieve over time. Sometimes we are slower than we would like,to attain our goals but we get there with perseverance.
I hope my sharing of my life experience helps a little. But certainly if you are concerned about your memory and it gets worse please don't hesitate to consult a medical practioner as we are all different.
I love your green pea avatar - it is so adorable
xx