First i8u3z, your mistaken when you say your a coward or too scared to take your life. The hard facts, and I hope I don't offend anyone on here when I say this, is suicide is the cowards way out. And I don't mean that in a tough manly way but in the simple fact that sticking to the hard life takes more effort then calling it a day. If your living with these feelings then you should look at each day as it truly is A Triumph over them.
You say your a terrible person who has lied and cheated and hides the shame of these mistakes. Pointing out when someone is incorrect, especially someone feeling as low as you doesn't give me pleasure but I'm afraid you are because terrible people don't feel they are terrible people. Beating yourself up over your past mistakes isn't healthy, but it demonstrates your feelings of guilt. Another feeling you wouldn't have if you where truly as terrible person, but holding on to these mistakes isn't helping you. You have recognized you have made them, and clearly punished yourself mentally for them, so now it's time to move on, mistakes are part of life hell they are the only way we learn anything really.
There is nothing wrong with you if you feel uncomfortable around people (something everyone feels to some extent but lies about) and when your around the right people they will understand that and be cool with it.
When your depressed you become unmotivated and disinterested in everything, do not mistake this for your personality! as it leads to a cycle of self hatred and more depression. This may have been your personality for as long as you remember but that doesn't mean it will be you in the future allowing yourself to think this is the only way it will become true.
I'm not a medical professional, hell I'm nobody and I'm not going to have the magic answer because there isn't one but there are ways to channel these emotions to productive ends, music, art or writing. Depression feels numbing but in reality your in pain trying to express these feelings through another medium can be cathartic and help relieve them somewhat. This can also help give you a boost self-esteem wise as your doing something productive.
I'm sure you've heard all this before and I have gone on for a long time here but I'll leave you with a quote from a song I feel drives home a point people forget,
How hard is it to decide to be in a good mood,
And then just be.. in.. a good mood?
That's all I have to say because it's a straight up fact,
You control your emotions it's as simple as that"
next time you feel down and the negative thoughts start flowing, take a breath and tell that part of you to shut up, (it's what I do sometimes)
your that master of you don't forget it!