feeling like a bad mom

my son is always on the move..ALWAYS. If we go to the store, he went just stay by my side or sit in the cart..I have to buckle him in. granted he's 2.. so maybe that's normal. but he won't did that anywhere..Dr office, dmv, post office, gas station... if he's with me, he's running amuck. he doesn't listen to me. if I'm in line at the post office, forget it..I lose my place because he won't stay with me or near me.. at the dr today, he ran all over, cried to go in the exam room, screamed when I took the check out paper, and just generally won't sit still. at home, I handle this busy behavior with games, his abc board, number flash cards, dancing.. but in public, typically I'm busy.. I feel like I should have more control over him but I'm struggling and I feel like a bad mom. I'm with him ALL DAY EVERYDAY so I don't know why I'm having this issue. He's smart, he knows his letters, most of his numbers, colors, and a lot of words, so I know he can understand a lot.. any advice?