Helenhull, I think you are right to be concerned. It is never a good thing for a baby to lose weight, and the fact your dd looks skinny at 10 weeks is worth worrying about....sorry to be so frank, but it's better to be honest, I think.
You need to speak to someone, prob more than one person.
You need to speak to someone who knows about bf, and about how to support it and increase it through a crisis - the phone lines given here will help. It is not good that she is feeding so infrequently - a baby who needs to gain weight should be waking in the night, not dropping feeds.
You also need to speak to a child health specialist - could be a good HV, could be a good GP, or a paed - to check out your baby's health, as there may be reasons other than lack of calories underlying your baby's weight. I am assuming your GP has reassured you your baby is basically well.....though to be honest, you might want to seek another opinion about that, unless you are sure the appointment is gonna come through quickly.
What does your HV say?
How has feeding gone since birth?
Hope you can reply, and you get some good help soon.