My best friend of 4 years wants a romantic relationship with me

I (17F) and my best friend (17M) have been friends since eighth grade. A month or so ago, he confessed to me. He told me that over the summer he developed romantic feelings for me and asked if I would consider dating him. I told him that I felt like we should just be friends.

I told him he's one of the most important people in my life and I don't want to lose him even though I didn't want to date. I talked about how I had thought about the two of us together and it didn't feel right to me. On all accounts we make sense, and I couldn't figure out why I wasn't feeling attraction to him. In the end, he said he would be fine and he respected my decision. But I could tell he took the rejection pretty hard.
Things went on as normal for a few weeks. We would text and hang out, everything was the same. I thought it was fine. Here's the thing: Last night at about 1 a.m., he texted me. (I'm visiting family for New Years and when the text arrived I had just gotten to their house.)

He talked about how since the rejection, he's been in a weird spot. Here's one excerpt from the text:

"[You] sorta rejected me, but not really and [you] told [me] we would make a good couple or that I was too important of a person and how you thought of us being together. [And] I tried moving on multiple times. each left such a bittersweet taste. and so I couldn’t and it kept replaying in my head."

He also spoke of the reasons he likes me as a person. He said that he loves everything about me and that he doesn't think he'll ever connect with a person on the same level again. And then this line: "All this to ask can I be your boyfriend?" He said he wants to stay close no matter the answer, and that he was sorry for suddenly pinning all of this on me.

He's such an amazing person and I care deeply about him. We have a deep emotional connection, as well as open communication, but no matter how hard I've tried, I can't feel attraction to him. I see him as my best friend. I don't know if I can develop romantic feelings for him, but I want to give him the closure he needs/wants. I don't want to hold him back, and I honestly don't know how I feel. He's talked about how much he wants to devote himself to one person, and I don't know if that can be me.

Personally I've been going through a lot as well. I recently discovered my bisexuality and I've been stressed about coming out to my Christian parents. I've been in a low point as far as mental health and stability. I've never been in any kind of relationship before, so in all honesty, everything about this situation scares me.

Edit: Not to mention that I've been struggling to feel real attraction to anyone. It might just be the stress of everything else. (End of edit)

I don't know what to do or say. I don't want to lead him on if I truly don't feel attraction to him. For now I told him I would talk to him about it after our winter break is over. I don't want to make him wait forever.

I need advice. Anything is welcome.