Moms I need advice.

I am a single mom and I have a son who is two. I noticed that when we get around other people or go into a new environment, he starts to act out. He will cry and throw tantrums and won’t stop until I give in. I put him in timeout and he doesn’t stop crying until I give in. I try not to give in but there’s only so long I could wait until his cries start to bother people. Because of this, I’m scared of taking him places and having him around other people. I don’t know what to do to keep him from crying so much. Things that trigger his crying: having to share with his cousin, people picking him up, not having all of my attention, not getting his way. It’s not the fact the he cries, it’s that fact that he cries for so long and won’t stop or budge. When those moments happen I feel very judged, anxious and overall like a bad mom because I just don’t know what to do. When it’s just us, he’s very cooperative, much more easy going and his behavior overall is good.

What am I doing wrong? What are some things I could try?