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I have/had anxiety problems in university and what helped was taking fewer courses because if I got held up with something or if anxiety related problems slowed me down, it helped me to know it wasn't the end of the world because I wasn't falling behind on what felt like literally everything. Is it possible that you can drop a course? Yes, no maybe? I know many people who couldn't because it would affect their financial assistance, which they needed all of, but if you have a diagnosed anxiety disorder like me, you can sometimes get accommodations to take fewer courses and still be technically considered full time so it won't affect financial assistance.

Since it does sound like your dealing with a lot of stress or anxiety that you don't have a good handle on (I say so because you're describing it interfering with your ability to do your work), you should also consider counselling. Many universities/colleges on site to help students with anything and everything under the sun, and if they can't they'll refer you to someone who can. So that's a great place to start to get help.

Finally, you should access academic support groups; I am not sure what they'd be called at your school, but most campuses have places you can go to develop studying skills, essay-editing skills, etc. and they're super helpful.

If you believe you have an anxiety disorder, you might want to consider getting a formal diagnosis so that you can access disability related learning assistance at your campus and they'll really help - without the help of these people at my school, I seriously wouldn't have a degree.