Miss natalie - sounds like you are having a really tough time of it!! i can totally sympathise with the lack of sleep / crying at the slightest thing / snappiness you are talking about - it sounds like you are describing me!!
I have found that talking to my partner about it has helped (he has been snappy too!) we are both suffering from tiredness - so he can understand to some extent what I am going through.
My daughter used to go for 4 hours between feed - almost set your watch by her! - but more recently has been wanting feeding anywhere between 1.5 to 3 hour periods. This is a killer through the night! One thing I do to help me is staying in bed till later in the day.
So, if I have been up at 1am, 3am, 5am, 7am, 9am with feeds - I try to get straight back to sleep after each one, and will continue to feed and go back to sleep till I feel ready to get up............ sometimes won't be till 1pm!! but I reckon it's definately worth it coz for the rest of the day (short though it may be) I feel tons better!!
Also, have you tried feeding Henley in bed with you lying down? that way you can kind of doze whilst he is feeding? I spent a whole day doing this last week and it was V relaxing!
hope this helps - obviously I am no expert - but just thought I would let you know what has been working for me - and these are just the ramblings of another knackared first time mum!!