I get irritated and angry very easily.

I have been experiencing anger and frustration in extreme levels. So much so that sometimes I get so annoyed at myself that I end up hurting myself, physically. People around me don't understand what I'm going through and I don't know how to explain it to them either. Because of this my relation with others is hampered. I get irritated at very small things, be it something positive or negative, even if someone cares too much I end up annoyed by them. I have been feeling this way for quite sometime, maybe about a year or two, it's just getting worse and worse. I'm not sure what the problem is but I end up feeling guilty and I cry for hours and hours. It takes me days to feel better and happiness just doesn't seem to stay within me. I'm always glum and sad. My mind is filled with negative thoughts all the time. I feel like I'm depressed all the time. Please help me. I really need it.