Well you are not alone. A lot of people are suffering from it too. There are different ways peoples study: different environments and different techniques. First I would say... Try to remember how You used to study before the pandemic began. Like what motivated you... And next try to repeat that.. If that doesn't work try this... Usually if you aren't in the mood to study, you can bring the mood from it by doing actual activities that make it seem like you are studying. For instance, you could just start writing what you umderstood in Biology, or history subjects... What you remember. The idea is not to make this your study method. Due to the lively nature of writing you will be more divulged into reading and that mood you are talking abt will come through time. All in all try to make your study time enjoyable, fun and rewarding. I think it will get better and better.