Remember that passing is still passing. The scores you have are passing. There's a saying in my program: C is passing. C's make RN's. In my second and third quarters I dealt with having a pretty bad concussion where I could barely remember things immediately after I read them (if at all). I still have remnants of this concussion (my eyesight is forever altered, and I cannot test in a group), but I'm pulling myself out of it. I'm not sure how far into your semester you are, but you will gain a stride. In the meantime, do not be too hard on yourself (I'm famous for that too, but having the concussion taught me to relax and be happy with my hard work even if it meant I did not receive an A). Nursing programs are much harder than traditional college so realize.. you are passing! You are making it happen. Look at you go! You got this. You can do this. Make little cards and put it on your mirror saying "I am successful" "I pass this quarter easily" et cetera (however you want to say your self-affirmations). Look at them every day. Start by looking at them and saying it out loud to yourself every morning. Do it before bed... and do it when you are feeling down. You will feel a little bit of self-empowerment. Try it, it at least worked for me.
Study wise: try something different. Do something to switch it up, perhaps you are getting bogged down by too much of the same. Change the venue, or give yourself a treat. Change the music in the background... I feel myself get into a rut and I stop being able to learn as much. When I change the environment and approach studying differently (maybe you always read first then do videos and notes... maybe switch it up and do videos first then read for example). I'd need to know more about your learning style to really make specific to you recommendations. Also, try to go over NCLEX style questions before and after studying and before and after class. This will help adapt your mind to how to use the information.