I completely understand being stretched in so many different directions. But you have to take care of yourself, else you can't take care of others.
In the beginning, when D11 first started school, I didn't sign her up for any activities but dance, and I was not an involved school mom. I mean, I showed up when all the parents were invited, but I did nothing extra. I was such a failure, I couldn't even get my daughter into girl scouts! That was where lots of the friendships were made, between parents and kids.
In Kindergarten, my daughter luckily made an instafriend and brought us parents close together. They are besties to this day. I am good friends with their parents, I just celebrated their 50th with them. They brought me close to the parents I didn't know existed in my town, who are my type of people. We all drink , curse, and love our kids fiercely. It's completely the no judgement zone. I always felt like I might be judged for being the single parent. At that birthday party, everyone said to me, men and women alike, how much they admired me for buying my house on my own because they know it isn't easy and all genuinely offered to help in any way that they could.
Start small. find out recreational activity your son would like. Not one that takes up a bunch of days a week, but one day a week. be confident in yourself and invite the other kids over. A birthday part is a great way to help him make some play date friends too. The best part? When he gets a bit older, you send them over, you get time to yourself! You help each other out when you are in a bind. Me and D11's bestie parents are always helping eachother on snow days, delayed openings, practices, whatever it may be. It's great.
Find your tribe. You will. You are doing just fine. It all becomes overwhelming, I understand. But remember you are more than good enough.
