how do you get out from study’s anxiety?

I was a really study student at high school, I was like a war machine even if it means to demolish myself it always was the studying first but since I finished high school (two years ago) and I started to attend to university I can’t study anymore, I can’t concentrate, I always have headaches, my heart beats fast and I don’t believe in myself. At first I thought because I was tired from the high school but then even after I took a gap year first, I can’t do it, I can’t pass an exam and since now I have to attend to the second year I will have the exam of the first year to recuperate first and my anxiety increases even more.
The main problem is that I can’t organise correctly the time I don’t know how to study so I pass all day trying to study but in reality I don’t achieve nothing because I don’t really concentrate.