I feel like theres nothing I can do and its beginning to show?

ok my ex broke up with me a little over two weeks ago before we went out we we're best friends while we went out we were even closer and now were just back to being best friends.......simple right well heres where it gets a bit tricky.... alright so she called me the day after we broke up twice which seemed weird to me..... I tried at school the whole not sitting at lunch with her deal....I failed.....tried moving on.....failed.....some how I just can't move on.... she's my best friend and what not....and trust me she throws that term out alot as well with the whole "Best Friend" deal. I seem not to say anything back because I still do like her but am afriad that if I was to say something I'd screw up what I've fixed over the past couple of weeks. However she still gives me hugs, wants me around her, calls and texts me, and has even talk about when we dated which is kind of akward because I am the type of guy that is kind of shy and what not and doesnt express my feelings and emotions as much as I should. My other problem is prom is comming up in April and I want to ask her but am afraid I'll screw up I just feel confused she's my best friend yet she doesnt act like anything has changed its like we're going out still but not holding hands and ect. if you know what I mean....My ex also has this other friend who I know for a fact is a "sleezebag" that my ex is now started to really talk to. As a guy I despise my ex/best friend/crush/ whatever's newly found friend for the soul reason that she might be telling my ex to just screw with my mind to make me hurt more....or even worse start stupid rumors about me. I put up with this about almost everyday due to the fact that I sit with them at lunch. yeah yeah yeah I know well why dont you just move because I have no one else to sit with. Just yesterday she asked me to call her because I had stopped calling her so I did and she texted me saying "she was mad and couldnt talk because her sister had mad her really mad" So today she tells me that her sister made her mad about guilting her about everything and guilted her about how she hadnt been a good friend to me this year and had treated me like absolute crap. This struck a nerve with me because I relized that her sister was absolutely right! So I decided not to say much for the rest of the day. When she asked me today what was wrong I said "Nothing" of course she could tell I was lying X( I planned for tomorrow just not to say anything at all to her but just to nod my head or say stuff like yes or no or maybe or I dont know. Simple stuff let her find out whats wrong with me on her own im sure she already knows though probably but I dunno I just need some good advice I'm doing all I can my ex/best friend/crush/whatever is a very very clean girl aswell so you can see why im worried and I feel that this is also starting to effect my thoughts and health as well I feel sad annoyed angrey depressed ect. all the time I stay in my room all the time and have just gone off on my friends lately. Help I feel like im going through depression and random amounts of anger.