apology to an ex

not gonna lie, this is long: i broke up with my ex about a year and a half ago because of a shitty reason. he was going through possibly the worst time of his life due to his very severe anxiety and i felt like i couldn’t help him. he made me feel like shit because of it and just rubbed me the wrong way towards the end. i realize now that he was going through a lot and although it was unfair of him to take it out on me, i shouldn’t have treated him the way that i did after we broke up. i completely ghosted him, blocked him on all social media and his phone number, and just never explained to him why it was over. i just couldn’t face him. now i’m in a somewhat new relationship and am being treated better than i ever have in a really long time. not only does he treat me with so much love and respect, but he has taught me it which has made me realize what i did to my ex was wrong. i feel like i should reach out to him and apologize because i think about what i did a lot, but i don’t want to upset my current boyfriend or open some can of worms that starts a lot of drama in my life. what should i do? i know in the past he has reached out to me to talk about it in person, but that just makes me too anxious myself.

TLDR; i treated an ex badly, my new boyfriend treats me wonderfully and makes me realize i need to apologize to my ex.