Typical 3 Yr old vs ADHD

I have a very active 3 year old who is always on the go. He can sit and watch TV or sit a listen to a story but he does get bored easily and is very indecisive. I've always just thought he was an active toddler. Nursery have started calling us in to talk about his behaviour and now I'm worrying that I'm missing something. He gets to the afternoon/evening and it's like all of his energy has built up and he needs to get it out so gets really silly and makes bad choices. He watches too much TV and I accept that. He's got a 1 year old brother and I've used TV over the last year to survive. I worry that this is playing a big part so we are starting to cut down. Has anyone gone on to try and get an ADHD diagnosis? I dont care if he has it but I dont want to be thinking it's all normal for his age if I'm missing massive red flags that I can get help for before he starts school. Just feeling like I've let him down and I don't know what else to try. He gets lots of exercise & eats really healthily. He is petrified of the potty so is still in nappies but we are making some progress. He doesn't listen and it drives me insane, he's also really emotional so when we tell him off he gets really upset. I work shifts and I feel like he has got worse since I went back but he's also getting older so could be coincidence. Im just lost with it all and don't know what to think anymore