Dealing with strangers

Just want to get it off my chest. Today was an extra hard day, he was in a great mood but was very loud and rowdy at the doctor. Running from me, laughing/screamjng, and just would not listen for his life. I tried to keep him on my lap in the waiting room, but he kept screaming and trying to go upside down. Of course I get stares, but an older lady behind us kept scoffing and muttering for me to shut him up. After a long and already hard day and having to catch him for the 5th time, this was the first time I’ve cried in public. I really have been trying lately, but it’s like when some things are easier, other things get harder. How do you not care about what others think? I am constantly overthinking and taking to heart every stare and comment.