I need advice on how to tell my friend I have fallen for her?

I have been struggling with this for months now & I have finally decided to tell my friend how I feel. I don't know what she is going to say but I have the feeling she already knows. Here's a little of whats been going on so you tell me does she feel the same? My Best friend is the most amazing woman I have ever met & yes she is a . Ive never had feeling so strong for a woman, I have always been straight so this is new to me. No I am not bi curious & I don't think about other women ever... just her. We definitely have a connection between us. This past weekend we were out & a mutual friend asked us whats going on with you two? We didn't answer... did he notice it? She is always in my personal space & I do not mind at all. She puts her arms around me , compliments me, teases me & has made suggestive comments in a way that she sounds like shes kidding but I can feel the energy. When I look at her or we have pictures taken together we are always close & is it true about pupil dilation? I have been reading everything that I can to see if I can find out if she feels the same. I know the easiest way would be to ask but it's not that easy. She is my best friend & if I ever lost her I would be miserable. We had to sleep in the same bed this weekend (no nothing happened) But both of us were awake all night, I think we just pretended to sleep. We were close together & neither of us flinched. We had a picture taken & for some reason she decided to put her leg around my neck, I was grabbed by another woman which I didn't like & she knew I was uncomfortable and asked me would it be different if it were me who did it? seriously I feel like she has the same feelings for me but we are both to chicken **** to say it. I sent her a text yesterday that said I needed to talk to her about something so she knows I have something to say, I think it should be in person tho. Please only serious responses I need to know how to address this. I am scared I am almost 40 & this is the last thing I expected but when you know you love someone there is such a strong feeling in your heart it is gut wrenching. I have cried my eyes out wondering what to do. Please someone tell me they have been through this & how I can get through it without feeling like I am getting my heart ripped out.... :(