How to tell my mom I had sex

So my mom and I are super close and she said she wouldn't be that mad if I had sex but there's this guy I've been talking to for a couple weeks and I met him last night for the first time and we just instantly clicked and it was so amazing. I'm only 14 but we had a really deep connection and basically one thing led to another and we got high (we both smoke so it wasn't a first time for either of us) and we just had sex. It wasn't his first time but it was mine. I don't regret it at all even though I had just met him we had been talking and it felt really special and just real with him. I just need to tell my mom, I know she won't be mad but she'll probs be disappointed I did it after just meeting him... I'm just wondering how I should tell her??