Ok. I think i shouldl first answer where you are getting problems as per my view.
I worry about my studies. >>>>>. Its obvious for you to worry but "Tension lene se kiska bhala hua he" You have to avoid it and make your mind accordingly. I use to remember aboutmy good moments of past whenever i feel stressful during studies and believ me this is 10% success funda for me I find it difficult to concentrate on my work. >>>>>> Concentration is must for anything not only in studies. You can go for Yoga every morning in early hours. It is well tested formula to keep your concentration level high. Further It may be due to continues reading so better to take a break in studies and then proceed. In the bereak time you can do whatever of your interest. but never make your interest in study sopil so take a break but it should be small. I understand my notes when revising. >>>>>>>>. It normaly happen with most of us that when revising the course we feel it was not read by me before but the fact is otherwise many times. It is not necesary that everytime you revise and read every new topic.