My best friend [21M] just confessed his feelings to me [19F], and I'm not sure how to respond.

We’ve been friends for about two years and share a really close bond, with many common interests and plenty of time spent together. I even think of him as a closer friend than some of my female friends. I’d be lying if I said I didn’t have romantic feelings for him and wish he felt the same way. A few days ago, while we were joking around, I teased him until he admitted that he loves me and has for a long time. At first, I was thrilled to hear that he loves me, but the next day, I started to feel strange and began to distance myself. I like him, yet I can’t seem to shake this odd feeling and remain distant. Is this normal? I would appreciate any advice on what I’m feeling or what I should do.