It's hard isn't it - finding a balance. I am the same, I yo-yo alot. My only suggestion is the calorie king site - (didn't you give me the link to it?) - you can select the maintain weight option when you fill out you inital diary thing. If you follow that for a month or so, you might get to understand what you can and can't eat to maintain you size.
I've been to a dietician in the past - very expensive and not particualarly helpful for me really.