Happy Christmas OP. I am sorry you had a shit time. Please let this be a wake up call. the way you treat others is the way you long to be treated yourself. Next year, all year long, starting from now, look after yourself and your son first.
I used to run myself ragged helping other people. I was worn out, unappreciated, had demands made and criticisms levelled when i couldn't fit it all in. I was pretty much working full time, unpaid, running errands and doing good turns and my relationship with my children suffered. If you've been raised to be a people pleaser, it's what you do naturally and it takes years to realise most people will never return the favour.
Stop now. Never volunteer your services ever again. If asked directly to do something, give yourself time to think if it is convenient. Direct your energies to improving your life - getting a good job or qualifications, making caring, kind friends, spending time with DS playing with him, reading to him, going out in nature.
Practise asking for help too. That can be a hard one. Start by asking organisations for single parents or by signing up for 6 free CBT sessions with NHS to help you become more assertive and less down.
You will be so much happier, stronger and more confident this time next year.