I would say stop weighing yourself. My appetite came and went through my pregnancy i'm now nearly 39 weeks and have only put on just over a stone - midwife is quite pleased with this, so i wouldn't worry.
The myth we are eating for two is just that a myth. Have your tried to eat fruit, when i was struggling to eat much fruit always went down fine. I woul also try to make sure you are drinking plenty.
If you are worried speak to your midwife next time your in.
I'm almost 35 weeks & have put on 10 pounds, with my last pg I put on 15 pounds in total, don't worry about it. Bub will get all it's nutrients anyway as long as you keep up fluids & try to eat little & often of whatever you fancy. I'm currently eating Angel Delight like it's going out of fashion. GP told me it's better to eat something than nothing as long as it's not Big Macs etc every meal, every day baby will be ok.
Widgetsmummy, so glad to hear that you have put the scales away. I bet you wont worry as much about your weight gain now.
I also have a case of first time mummy-itis, lets hope it gets better. It's so hard not to worry, esp when you read how it is 'supposed' to be in all of the books. I've also packed my pregnancy books away and if I have any worries or problems I come on to MN to get advice and help.
I'm too scared to get the scales anymore!! I'd put on 1 1/2 stone by the time i was 20 something weeks! Saying that, i was low carbing prior to becoming pg and then when i found out i kinda went on a bit of a carb fest so that's probably why i put on too. I dont intend to weigh myself now til i'm at term (if i'm brave enough!).