That sounds really rough.
First of all please go and find something to eat, anything. It'll make you feel so much better.
Secondly find someone to talk to face to face about all this. Can you talk to your girlfriend bout this? Family? Friends? Counsellor?
And don't be hung up on possibly having a mental illness, although I appreciate how hard it must be to accept that. The first thing to know is no matter how rich, powerful, famous, smart or not any of those things you may be...you're susceptible to a mental illness. I'm assuming you haven't seen a Doctor yet?
About ADHD. You usually develop it as a child. Did you have the symptoms of ADHD as a child? If you can think back that far. No offense but your description of why you think you have ADHD isn't very convincing, so don't narrow yourself down into that. You may have ADHD for all I know but don't self-diagnose...go to the appropriate people that diagnose you. Here's a page that may help...however maybe it's best if you read it tomorrow when you're feeling better.
http://www.nhs.uk/Conditions/Attention-deficit-hyperactivity-disorder/Pages/Introduction.aspx
If you do end up having ADHD then you've made the first step to managing it by realising you may have it.
Sometimes it's these low points in life that become turning points for us. I hope you feel much better tomorrow :)
