Cutting is a result of your depression. Hurting yourself seems to be the only way of relief, BUT it is not a permanent  solution to darkness you experience. Depression can be and usually is a clinical issue. It is when the chemicals in your body get off whack. I have a similar disorder called GAD and with mine, I was in denial. I would try to make it without drugs and therapy. I felt like it made me less of a human. The outlook on life is not the same as your peers. It is not the "norm" and this is b/c of the chemical imbalance. Does this mean you are weird? No. Does this mean you will always be as depressed as you are now? No.
People with OCD ( Obsessive Compulsive Disorder) may tell repeat words in their heads over and over again. They may ask similar to your question "Why is it so bad I repeat things over and over?" The reason why is because you do not have to live that way just "dealing" with your pain. The pain must be addressed. What exactly happened to you? Tell us on here. We don't know you and would be glad to help.
Hurting yourself is not a "normal" act. And this is what you must try to accept. People who don't have depression, would never think of harming themselves.  So its really important to find the solution to the imbalance going on. The drug you took was apparently not the right one. I would try seeing a psychologist about your problem. A regular doctor may not be able to help you as well.

i started after my grandpa died,he was really the only father i had-my real father was....not the nicest person.but when i was w/my grandpa,i felt safe.so when he died,i felt lost,so i started cutting.it always made me feel better.i get that its bad.......i just dont know how to stop.......