I'm a Wimp 😂 I Need Some Advice

I'm kinda hardcore crushing on my best friend to the point where I just can't get her out of my head. I really really really like her, but she's my best friend and I don't want to ruin our friendship. She's been going through a lot lately and I don't want to contribute to her stress, but I feel like I'm going crazy. I think I'm going to tell her how I feel but I don't know how or when. I don't even know if it's a good idea. I'd love some advice, especially on how to ask her and how to get over my nerves. I'm kinda new to this whole romance thing so anything would be appreciated.