Asking a girl out after a couple of months

Hey guys. These days I am a little sad and down because of a stupid mistake that I made. Now, I am here to see if there is anything that I can do to fix it.

I work somewhere and from the beginning days (5 months ago) I saw a girl in one of the offices near us. I liked her from the very first moment and knew it. I am not going to say I love her because it is to soon, but I definitely like her. Little by little we could initiate great conversations and almost within 2-3 weeks I had the best opportunity to ask her out. One day, she herself came into my office (for the first time ever!) and started talking to me. She even asked me if I want a cup of coffee. However, I was really stupid and I did not ask her out, don`t ask me why, but I just did not (maybe lack of experience, because she was the first American girl that I liked.). After that and till today, we always have good conversations (maybe less once a week or every two weeks), but I think I am kind of in the friend zone. But I think there is still a chance and that is why I am here!

Now, I really decided to ask her out, but the problem is that asking her out has been really difficult. I even heard that she may be in a date with someone, but I am not sure and I do not care. I know for sure that at least in that 2-3 weeks she liked me as well and there is a chemistry, and again, there is still a chance and hope.

I want to ask you guys, what should I do now? I am really sad these days and cannot stop thinking about her!