G.,
Given your previous questions, it sounds like you don't have a lot of support right now.
I cannot tell you what to do in regard to your son. Right now, it sounds like you need to take care of you.
Doing a brief Google search, here are some resources I've found in your area:
http://www.mhapbc.org/NeedHelpNow (hotline #-561-801-HELP (4357))
http://southcountymentalhealth.org/adult.html (they have a sliding scale fee and specialize in single parenting/parenting skills as well as other mental health care)
http://www.the-bright-side.org/site/thebrightside/content...
I want to stress this-- there is nothing wrong with calling a crisis line, just to have someone who can listen objectively and offer some empathy and advice. Many very strong people have done exactly that-- that is the definition of being strong, to me. Being strong means recognizing you need help and asking for it. I've called one of those lines when I was at the end of my own rope many, many years ago, and felt better when I got off the phone. Felt like, even though the situation was terrible, there was still hope that I would get through it.
Please, reach out. If you feel that you are having a breakdown-- and people do sometimes experience this, it's a signal that it's time for some thing to change-- get help. Find a counselor who can work with you. This is NOT all on you, but I know you feel responsible for it. Everyone has their part to be responsible for. Please, again, reach out for help. Only someone who can really talk to you can help you to know how to move through this difficult time.
And please, don't over-react to your son. Cancelling Christmas doesn't solve anything. Really, he already feels slighted, likely, by your boyfriend not giving him gifts and such. His attitude is likely compounded by that and not succeeding at school, feeling like a failure. My guess is that cancelling Christmas would feel like *even you* are thinking he's 'not worth it'. It won't be interpreted as anything other than a rejection of his person. My parents punished me nearly constantly, but I was still allowed to enjoy Christmas. Something to consider.