My mother went through very much the same situation; she had been a housewife for almost 30 years when my dad and she split and he was hell bent on not giving her a penny. My brother, at the time, was about 6 and she was so scared she would have to give him up until she could get her life straight. The truth of the matter is that you have rights...rights to keep your son, rights to get child support from your ex, rights to food stamps, medicaid, welfare, etc etc... as far as you finding a job start with something small since you probably don't have time to wait weeks or maybe months to go through corporate job search hell. Apply at restarants, department stores, banks (tellers get paid well and you get evenings, weekends, and holidays off garanteed!). My mom started off making $7 an hour as a cashier at a grocery store and then went up to $8 as a bank teller and has since moved on to a lovely cushy office job making $13 an hour...it takes time but you can do it! And you're still young so it's a lot easier for employers to understand why you have little to no experiance. (when you're starting the work world in your 40's people tend to look at you funny).
You can also look into a temp agency...I'm not sure where you live but in the New Orleans area there are some really great ones like Brooke, Adecco, and Kelly Services; go through Monster.com or the yellow pages to find them.
F., I wish you all the best of luck and if you need any advice from someone who has been through the dirt poor, searching for work, single mom hell too feel free to drop me a line.
Take care and keep faith