If I'm into two guys & they're best friends, who do I pick?

Okay, so I got myself into a bit of a situation. I(17F) am talking to these 2 guys, let's call them Mateo(18M) & Javier (17M). I met Javier through Mateo. I really enjoy both their companies and I like them, but Mateo confessed to me a while ago, and I rejected him because I wasn't ready for a relationship. I did tell him I find him attractive and like him, but I still had shit to work through. He said it was fine, and we're still close friends and we flirt every so often. Okay, and then I've been talking to Javier a lot as well. And after a while, I told him I was into him, and turns out he's into me too. We kissed and all, but then he remembered that Mateo is still into me. He felt bad for a while, and I told him to tell Mateo. Well, we're still hanging out and making out every so often but not too much on that. But the more I talk to Mateo the more I like him. I also really like Javier. I'm into both of them equally as much the more I think about them. Mateo also tells me my pupils are stupidly dilated whenever I'm around him. I don't know if that has to do with anything, but I think it's worth mentioning. What should I do? Javier keeps telling me to keep this a secret for now, and to not tell Mateo anything, but the more I'm around him, the more I want to kiss him too. I want both, but I'm unsure that'd be possible.