In need of advice

I'm teaching a community pre-k art class that I didn't terribly want to teach but my sister runs the program. I've been taking my toddler (almost 3) with me and he's a busy kid! But also super social. The other kids in the class just don't want to play with him or talk to him because they're more timid. Yesterday was bad. He tried saying hi to a little girl and she told him to go away. And this happens with another boy who is about 3 too. My son will talk to him and he just won't speak. He got stressed and sat out and said he was "waiting for his friends." I tried getting him to participate and he started telling me to go away which he's never said before to me until after that child said it. Anyway things eventually escalated. He threw a huge fit and distracted me from teaching. I yelled at him on the drive home which I never do. This morning he told me he doesn't love me. I'm also dealing with some health issues which stress isn't helping at all. My question is should I quit? I've only been teaching it since January and I feel bad cause it's my sister's thing but I'm so stressed.