Hey tamzin, I don't think it matters if you can't pinpoint a reason for why you are feeling that way (that is one of the things therapists are supposed to help you with)
If you say to the doctor what you have written here hopefully they will help you (I couldn't even say that when I saw them but I will have to try again. growl)

I wish you all the luck in the world and please let us know how you get on,

Bearhugs,
Fuzzy