Hi Judy, I hear you, relapse is always disappointing. But I can also hear how much you want to be sober & how much it means to you.
Can I ask: have you considered joining a sober support meeting? There are many options, both online and in person. I know as a single mom with a young child it can feel challenging to attend meetings while also caring for the kid (my mom was a single mom as well). However there are many meetings that are open for parents to bring their kids; ask around, there are women’s groups and mixed groups, the key thing is there are options where you can bring your boy with you. There is nothing to be ashamed of, and he will see his mom taking healthy steps for herself - which is healthy for him too - and he will learn from that 
Here are some online ones:
Online meeting resources
And here’s a list of more recovery programs (many have online options):
Resources for our recovery
It helps so much to walk the path with people who have walked it before. You will find meetings help you feel less alone and you’ll make friends and connect with people who understand you.