Hey, you're not alone. I ****ed up royally last year and have lost my career, the job I loved as a result. It really sucks, but it's life. Like you, I'm back living with my parents as I've lost my marriage and my home as well as the job.
I know the feelings of worthlessness, the lack of self respect and the despair at facing life, but we have to go on.
You say you have a son, well guess what, to him you're the absolute best human being in the world. He loves you absolutely unconditionally, and even though I haven't met you, I know you'd do anything for him. No matter what crap life throws at you, you have your son and your family and their love.
A lot of people would give up going through all the crap that you're facing, but it's obvious from your post that you actually care, you're someone who gives a ****, so I have no doubt you'll fight to improve your situation, as I hope to do with mine.
And as Jennifer has said, there's always people willing to listen and talk things through on here.