3 year won’t leave me alone for two seconds

I have a 3 year old and a 1 year old. My 3 year has always been extremely clingy. I cannot pee without him standing right next to me. My 1 year old is content, he will entertain himself with toys for 30 min to an hour by himself. I cannot get my 3 year old to play independently for more than 5 minutes. He constantly needs to be entertained and have me right there next to him. He’s always been like that and it’s become so exhausting. He’s right under me 24/7. What are some ways I can foster a little more independence in him? I try to explain “mommy will be right back. You stay here and play with your brother”, but he just follows me anyway. If I put up baby gates he climbs over them or screams at them until I come back. I love my kids dearly but I’d like to pee in peace for once 😂 Any tips?