I struggled with schizoaffective disorder when I was at university too and took medication for it. I think the psychotic symptoms can make concentrating difficult in themselves but the medication can make this worse - at least in my experience. Is there any way you can change medication? When I took risperidone I had difficulty working out 10% of a price in a store, it was ridiculous. However I now take haloperidol and find that I have a lot more freedom with my thoughts and my math skills, whilst still not at the level before I was diagnosed, are much better. Mood symptoms like depression can also affect how well you can concentrate and think so if you're finding yourself feeling depressed it'd be a good idea to talk to your psychiatrist about medication for that.
It's a difficult situation to be in I know , not knowing whether it's the medication or underlying condition. Are you receiving any help from your university? For instance the counseling service or DSA? DSA in particular can be a huge help and if you inform your uni you can get stuff like extensions on deadlines if you're going through a particularly tough time when you have work due.
Hope this helps. Good luck!