10 months stuck with ex, just wanna explode!

Uff so i am abroad a 10 month as a volunteer with my ex, she has another person not dating at least for now (but she is advancing way too fast). I am stuck in the same house with her(just us) and i get to see her giggling in video calls and stuff like that.
I get really upset and my mood swings to frustration and anger, so sometimes i bully her and offend her and his new "friend". I thought it would be easier but it doesn't seems that way, i know it's a childish attitude, but somehow i feel i need to hurt her because i just can't put a fake smile on my face (believe me i tried, it only shows i am not a good actor at all). Despite that, she doesn't want to leave me alone while we are here. Also she is always nice to me, we do our groceries together we share meals, go out for a coffee stuff like that, sometimes she hugs me when she understands when i'm down, and i don't really like it because she is damaging me even more.
Thing is she broke up before coming here, my feelings are really confused now and sometimes i wanna laugh and be cool with her but then i remember she broke up with me she is always on her cellphone texting and she said somethings i can't let go which just builds up and i wanna burst.

Any advice's? i'm only here for 13 days and i'm getting pissed off with this.

How did you get tied up living with your ex in the first pace? Was there a certain protocol that places ex's together? Why don't you just reside at another location for the next 13 days. Make sure you cut off a ties regarding communication with your ex. Then you won't have to put up with all the crap! But I personally feel you really like all the attention your current living setup provide.

My organization provides me with the apartment to live, i have no option, and i had signed the contract before we broke up.
I can't cut ties because i work with her, i did that and the office just got a bad vibe trust me. Past days, time impressed me with the ability to absorb and ignore but then... (and no i don't like the attention! + she spends more time crying now than giggling)

She insists on getting someone new (sex included), but doesn't want me to leave her alone, and if i get someone she would be alone here.
But i am starting to think she wants me to get someone to get even, or to kill any feelings left for me, I don't know.

Actually she got extremely jealous when i tried to hit a girl here, i knew her for a few days thought she was very interesting, many things in common and she insisted sitting next to me (very close). Everything was fine i was getting to know her, but my ex attitude and aggressive behavior towards her(her "I'm going to kill you if you touch him" Stare, plus some physical bumps), just made this new girl run away (we use to meet at bars and coffee all together among other colleagues.)
Guess she either thought that she was interested in me or that she was my ex, which she got it right!
Now she no longer replies to my messages, neither seems that interested of getting beated by my crazy ex.

Also to end, she said to me yesterday, that she wanted to have sex. Later said it was a mistake to say that, which i agreed.