I think going to the ER is still the best option, and definitely talk to your mother to see if she can help you with your son. Are there any 12-step meetings that you could go to? They say the recovery program is a "we" program, all of the steps say "we" and that's because we CANNOT do this alone. There are people out there (here too!) that want to help you.
Bad idea of taking the Xanax. Substituting another drug for the opiate is not good and will only delay, and possibly impede your recovery. Was it after you took the Xanax that you wanted to use the Percocet again? Benzo's can lower your abilities to think clearly and can convince your brain to use the narcotics again.
The only way I'm able to stay clean is to not have any meds in my home. Do you think you are ready to toss the percocet, and the xanax? You CAN do this, your son deserves to have his mommy. If that means going into treatment for a while, or just having your mother watch him while you're detoxing, then that's what you do.
I really wish you could go to an ER and let doctors safely detox you off all of the mood-altering meds. Praying for you!!