Mood swings

I hate my mood swings so much. I was happy. Actually happy. An then *bam* depressed. I was on a skype call with my girlfriend and it just hit me and I couldnt talk and I wanted to cry so bad and it was for no reason but I really wanted to cut and I felt so much hatred towards myself and I was dreading waking up tomorrow. Correction: I AM dreading waking up tomorrow. I hate it when I get like this. Because it makes her paranoid and she didnt do anything wrong I just feel like crying and cutting myself for no reason.