You know what, i totally understand and i would feel the same at losing 4lb hun, it's hard when everyone else is going on about 7 and 8lb losses. BUT!!!! Please don't give in now, you will have a good wi next week i bet you, are you near totm?
I could ask loads of questions to try and work out why it was a 4lb loss but nothing will make it better i know.
You sound like your head is in the right place for this diet which is excellent, alot of people would have thrown the towel in but you are stronger than that.
You did mention that you were constipated, have you had any luck with that?lol
You are the same height as me and your goal weight is similar to mine, we can both do it.
I have had weeks where i didn't lose much and it's rubbish but just think that's 4lb you will NEVER see again!
Good luck for your 2nd week and keep that motivation going!