A lot of text on this question, but here it is: Is it weird to ask for her number/ how do i...?

My question is: Would it be strange to ask for her number this early, and how would I start a conversation with her, via FB and/or Real life.

My LOOOONG STORY:

Ok, so there is this girl in my english class that I really like. She is all I can think about. I barely talk in class, and am VERY shy and always have been. We are usually in the same group in english, mainly cause we are all close to eachother (sit near to eachother, but are actually seperated by one person) so there is 4 of us. (I also think she may feel sorry for me, and she is SUPER nice).

anyway, I may not talk much in our groups either, once in awhile i would say something and they would kinda agree to it etc. Well, I messaged her on Facebook to get to know her, and to start off I asked about a homework assignment, then she told me what I needed to know. I then replyed thanks, how have you been? but she never replied. The next day, no reply and yet she updated her status via phone, I guess she never goes on FB on a comp so i cannot do a regular insta chat on FB.

Anyway, I then later (like a few days) asked her about a class she took tht I was thinking on taking etc. I asked a lot she replied a lot. then I said thanks and no reply etc. I think she is a busy person though, as she is SUPER smart, and is like a good student, and is very religious, and is in this Health Program otherwise known as HOSA. Anyway, what do you guys think? Should i ask for her number via FB message, or no? Some extra info: I have commented on her status before and she replied to it, and waaaaaaaay before all of this I commented on her profile about a pic of her, asking about her trip and if she was in HOSA because of this etc...I could tell she went to an amusement park.(the pic was her profile pic at that time). We are both Juniors in high school. I cannot stop thinking about her, like my heart dropped when she didnt reply to the how are you doing question, but I still like her. I feel I am a ugly person, (I got low self-esteem). I feel she is the cutest and most beautiful thing every!! My friend said shes ok...haha I dont care,

She may be a busy person, but she does check Facebook quite a bit, sorta, using her phone. Also, I feel there is practically no way i can talk to her, cause I am real shy, I have to get to know her before I can, unless she starts the convo.

Also, I want to text her as like a friend for now, but how would I ask for her number? Especially maybe via Facebook? I want to text her every so often so we can become friends and stuff.

I am soo stupid, I had a chance to talk to her today, but didn't!!! ARGH!!!

UPDATED:

SO I look at her profile pics because well, I like her, and then I see that everyone of her pics has comments on it with girls and enven some guys complimenting her and one guy said something about her smile in the picture etc. This made me feel that other people may like her, and so because of this I have no chance, because well, I aint like other guys who talk to her as much, or at all at some points, and who look way better than me. I feel like just giving up, or atleast until summer when I know we shouldnt see eachother then I will ask her out or something, or just for her number a friendly text her. IDK.

I know people are going to say don't give up, but it is like, I honestly do not think I have a chance...at all..... I always asked questions on here about girls and what not, and they all said I should ask, and I do, and get rejected, although I was stupid back then, like yea, it was good to try, but I didn't really get to know them first so big mistake haha. Anyway, yea, I am thinking maybe I should give up till the summer....i am not sure, part of me feels I can do this, but then IDK.

Sorry for posting this question many of times, I never got a 100 percent sure idea from the answers. Some say don't do it, others say talk to her (which for me is practically impossible right now, like I don't know what to say etc.) Everyone knows I don't talk much, but am known as a nice person I think. Other answers say to just ask for her number, and I know it would be easier via Facebook to get to know her and get her number etc.....ugh...IDK.