I know exactly how you feel!
I had one job so far and I only worked 3 hours a day from Monday to Thursday. I only did little stuff like stamp envelopes, deliver/open mail, copy papers and documents and stuff, sort things... etc. I've been trying to get a job for a while now and it just seems like nobody really gets back to me.
But please, do NOT kill yourself. ;__; It gets better, please, try and find maybe a little job like I did? That way you'd be getting paid at least and it's something you could handle?
I really hope what I'm saying is helping a little... I have problems talking correctly lol.
It'll get better, I promise. I was in the same boat, I almost quit my tiny job because I thought I couldn't handle it, but I DID. You can do it!