Rollercoaster day

This is ridiculous. My moods are so all over the place. Earlier on today I was really hyper - I was bouncing around and giggling, and generally being a pain in the arse and irritating my parents. Tonight I have been crying hysterically. I think my weird hyper mood started last night. I woke my dad up in the middle of the night because I was laughing my head off. He was fairly unimpressed. And then when I woke up today I was still in a weird mood. That probably lasted until early evening, and then my mood started to dip. I think it was largely because my mum had a friend over, which was fine in itself, but because of that dinner was weird - there was just all kind of nibbly foods all over the table when I went downstairs, like slices of pizza, and french bread, and lots of stuff I ignored because I don't like it, and lettuce, and cheese etc. Food being unstructured like that bothers me. I had some food, and then we took the dogs out for a walk (she had brought her dog over), and then when we got back there were little chocolate eclairs for dessert, and then later in the evening my mum got out cheese and crackers and crisps. By that time I thought fuck it, I have already ruined the day, so proceeded to have another slice of pizza, and a cracker with some cheese, and tonnes of crisps. And then I felt full and sick, and desperately wanted to purge, but couldn't. And then I just snapped. I burst into tears and lay on the floor crying totally hysterically, and just got more and more upset and told my mum that I hated myself and I was greedy and disgusting and I wanted to die. Way to spoil the evening for everyone. That was about an hour and a half ago now, and I have been crying most of the time since. I feel like absolute shit and I desperately want to hurt myself. I want to kill myself really, but if I am not going to do that I feel like I need to punish myself in some way for being such a disgusting pig. My dad kept telling me I was supposed to be on a diet, but I still kept eating. And now I will have gained a tonne of weight tomorrow and I can't fucking cope with that. My parents tried to tell me that everyone has days where they eat too much, and they just eat less the next day, but all I could think is that I have spent all bloody week desperately trying to lose weight, and now I have fucked up the whole thing by being so bloody weak and pathetic today. I just hate myself so much. I really want to cut, but my mum will be angry with me if she notices, and she is sure to notice at some point. I just feel so broken. I hate that food can have such control over me - that eating too much is enough to make me want to die. But it is. I just feel so terrible now. I hate myself so much. Everything feels so hard at the moment. It is like I am walking along a tightrope, and it is scarily easy to lose my balance and go plummeting down.