Can only second the advice given in this thread, despite only being of young age (19) I have had a few moments of depression, and the like, some worse than others, not been to see anyone for 'professional' help, just relied on close friends to help, if these feelings are a regular thing, and from your opening post sounds like they are, it may take some time for them to fully go.
I have been through suicidal emotions, and periods of self harm, and those feelings will never be fully gone from my head, its just the way I cope with them, and block them out. I hope that if you decide to go see someone, that it will help your mental state, its not a nice place to be in, and hey we all deserve abit of happiness from time to time