I need some help?

I don't want to be here, just found out my boyfriend lied to me about something. He didn't cheat or anything but he promised me he wouldn't smoke pot.
And I asked him today if he has been cause I was suspicious... he said no and promised me, then I found out tonight he smoked tonight. Dick. What should I do? Can anyone help me?
Btw he didn't tell me he did, I found out because he left his facebook open on my computer and I saw his chat.
I can't sleep, I need to be up in 3 hours but I feel so sick in my stomach over it.

I just want to disappear away from everyone, it's getting too hard. I'm suffocating myself with all the endless thoughts..drama..problems..decisions.

I weighed in tonight at 48.6 kg. So no gain from this morning which sucks, seeing as I ate barely anything and went to the gym.

Oh and tonight on the way home in the car, I started balling my eyes out for no reason my mum was just talking to me about Uni and I was telling her how busy I am and how I don't have any time to get new shoes for myself and I just got so emotional. I hate this.
Mum wouldn't leave me alone, saying how much she cared and why can't I tell her what is wrong, why are you sad? is it something i've done? she said. I blocked it all out, something I'm good at ignoring my problems.

Point of this post...I just want to die.