You sound exactly like me. I'm 25 and don't drive. I was always afraid to go to bed as a young kid, and had night terrors. I was afraid of people breaking in and fires mostly. I also have social anxiety, which I'm trying to work on right now.
The first thing I must say is your son would definitely not be better off without you. He loves you just the way you are. Second, I've thought that so many times. I've wondered what the point in living is, when all we do is get older and sicker, destined to die anyway, and in the process have to lose our parents and loved ones. Sounds to me like we're already in Hell sometimes.
But then I try to think of something positive, like just the past year. If I'd have given up life last year, there are great things I'd have missed, just in the past months. Believe me, I understand your struggles, but I feel there's always hope. Tomorrow is another day. If nothing else helps, at least live for those moments that are few and between but are wonderful. (:
I wish I had something better to offer, but being in the same boat, I don't.