This is going to be long I apologise. I feel really down about this situation, just want to know what to do one way or the other and stop feeling depressed about it. Also it helps to just type it all out.
This girl I live with at uni has been my friend since the first few weeks. Towards the end of the first semester I played with the idea I might like her. She's really pretty even when she's just sitting around in her PJ's and I really like her personality, she's basically as weird as I am. We've always flirted a bit just being jokingly mean to each-other. When we came back 2 weeks ago for second semester we got on even better than before...Over the first week I realised I definitely do like her and started to flirt more. I was pretty sure I could tell that she liked me a bit, even if she hadn't actually though about it. Just by the occasional looks she gave me and her flirting with me. Also, and importantly for where this gets less heartwarming, we'd disagree a lot in conversations, and she'd get really worked up at me. However, she never gets as worked up at anyone else, even when they argued with her more than me. So I thought maybe there was something there.
This is where things fucked up though. Last weekend she started being a bit off with me. If anything she was more flirtatiously mean when she spoke to me, but also she blanked me sometimes, like just sat in the kitchen and said nothing when we normally talk easily. Stupidly my response to this was to up the immature flirtation. Then she started getting in moods with me, and I felt like she really hated me. I said to her that I felt she was annoyed at me and wanted to go back to how we were before but she said she was fine. Like a total dickhead as she continued to be off with me and not say anything I just resorted to winding her up like a 14 year old who likes a girl but doesn't know how to show it. So like 2 days ago now she reached a point where she definitely was pissed off at me.
Things got worse yesterday. We were in the kitchen with 2 flatmates, she'd basically ignored me all day. She said that she was going for coffee with this guy she'd been flirting with last semester, and I said I'm going to me room and walked out feeling really depressed. Basically upset that she didn't feel the same way as I did about her but also hating myself for being such an immature prick the last few days, which probably blew things with her if there ever was something there.
Last night we went out, she was completely off with me, basically blanked me all night. At one point she was standing next to me, saying nothing, I felt really awkward so I poked her chin (I used to wind her up about her chin and do that). Now I realise that she had dressed up and looked amazing, she came over and stood next to me even though we'd been wired with each other, the last thing she deserved was for me to immaturely poke her in the face...But I did because I'm a total idiot. Then she just walked off after some other people we were with. I followed for a bit, but felt like such a prick I just decided to walk home.
Drama continues...
Today she didn't say a word to me even though we had to do loads of stuff together with everyone else because we were sorting out our house for next year. I'd sat in my room feeling depressed hating myself all day not bothered to go to lectures, she knew this and that I'd gone home last night. My mate came and spoke to me this evening, apparently she told him that she thinks I fancy her. He didn't really expand on it and I didn't say that I did. Also apparently the day before she told his girlfriend that she hates me.
I'd decided that I was going to apologize, just say that I'd been a prick and she didn't deserve to be treated like that. But when my friend text her asking why she hated me and saying I wanted to apologize she said I don't need to apologize for anything.

Now I'm left feeling terrible. I hate myself, I still really like her, and I don't want to go on not talking to her because it screws up the whole flat.

Also I can't help but ask, is she just really embarrassed that I like her and pissed off at me for messing everything up. Or is she pissed off at me because she though she might like me and I screwed it up? Does she still like me?

I definitely need a girl to tell me what's going on with her. Then I can either go back to being friends and pretend I never liked her, or I can try and tell her how I feel.

Added to this I'm living with her for a year and a half...I don't want to mess things up. And maybe she's reluctant to go out with me for that reason?

All advice is greatly appreciated sorry for the length of this!