Best friend + romantic relationship

I started seeing my best friend in a different light. We’d been going out more often together and we’ve been inseparable. I mean, we ARE best friends. For a few months now, everyone’s been asking if we’re dating. It used to be annoying, but now we just kind of shrug it off. Yesterday we went to a quinceañera together and he would lean his head on my shoulder, then later not-so-subtly try to put his arm around me when we were sitting together on a couch. For the past week, I’ve been kind of lightly hinting that I like him to see if there’s any response. Exactly a week ago we joked about dating on Snapchat but I know there was a part of us both that wished we actually were. Very recently he confessed that he liked me as much as I did him, if not more. I’m very happy. And suddenly everything fits into place. Everything makes sense. The way he would steal glances at me when we took care of the children at our school’s day care and then looked away; the way he always chose to sit next to me when there was a large group of his guy friends in the same room. But I digress. The reason I’m writing this is because I’m afraid that if us being an “us” doesn’t work out, I’ll lose him as a friend. I’m afraid that when his ex (a very dear friend of mine who still has feelings for him) finds out, she’ll be hurt. I’m afraid that my girl best friend might be mad because she already doesn’t like him as it is. I’m afraid of so many things but I want to be with him. I want to be his girl and I want him to be my man. I want him to hold my hand instead of us having to hide how much we care for each other. I want the cheesy things from the movies and I can’t have those without hurting people I love. He said he wants me to be his girlfriend and I will say yes when he asks, but I feel like I’m risking so much from just accepting. Has anyone ever been in a similar situation with a best friend and has any advice?