Hiya,
I think something must happen when you reach 6 weeks that has you reaching for prozac!
I too felt the same around this time. I went into Waterstones and started flicking through books on pregnancy and felt really overwhelmed. I thought heck I'm not ready for this. I felt awful that night but then the next day worried about miscarrying! I was all over the place. I'm 8 weeks now and feel a lot more balanced emotions wise. I'm very tired and sometimes feel ill after eating but I feel euphoric again about being pregnant.
Good luck and I hope these crazy emotions pass soon.
Take care,
S