HELP! I (23M) think I’m falling in love with my female best friend (23F)

So me and my friend have been close since high school (we are in college now) and despite her being attractive, funny, smart etc. I never looked her in other way than a friend. She shortly dated one of my friend who I’m not in contact anymore and my other friend tried for years to be with her, and I did try to make them date but she didn’t want to be with him. I guess all that did have some impact on me to not look at her as anything other than friend even though we really would make a great couple.

Anyways, lately we were hanging out more (at least once a week) and the last time we were together it just struck me. She’s been single for a long time, and I recently got out of a toxic relationship. Why wouldn’t we be a great couple?! That same day she proposed the infamous “if we are single at 35-40, we will date” pact and I accepted. I picked it up as a joke and brushed it off as she often jokes that we look like a couple. But as we got home, she sent me a message that she was surprised that her sister told her we looked like a couple on Ig story she posted even though it was just ordinary selfie. Lately only stories she’s posting were our pics when we go out (and somebody always confuses us for a couple, be it someone from her or my followers).

A few weeks ago it was her birthday party and I noticed that I was only happy if she sat right next to me and that feeling was at the same time both beautiful and awful, since it did imply that there is romantic feeling but I’m not sure if it is mutual and I really don’t want to hurt her if it isn’t. She of course posted us again on Ig story, this time with her dog. Comically, photo looked like we were looking at our baby, all 3 of us hugged, close together, smiling… MY GOD, did that photo make a mess in my mind. For a couple of days I couldn’t help but think about our future. So now here I am, totally confused about everything…

So there are 3 problems:

1. I’m not 100% sure that I’m in love with her or I’m just confused
2. I’m not sure she feels the same right now or if she even would feel if I told her
3. If it all failed, we would certainly still be friends, probably not so close as now, but I don’t want to hurt her (I’m willing to hide my emotions for her till they fade away if that saves our friendship)

**TL;DR** I think I’m catching feelings for my best friend as our friendship looks like a perfect foundation for a serious relationship. But I’m not sure as there was never initiative from either side, and now when I’m falling in love I’m afraid I will lose my closest female friend to some mixed feeling…