Hi Gina. Sorry haven't posted so much over the weekend. I read up on the latest, sorry to see you're not feeling too positive with the feeding, but well done for hanging on in there.
I'm with truthsweet re. offering the boob when they cry (if it wasn't cold, soiled nappy, obvious tiredness etc). Other people will tell you 'you're making a rod' etc., but I just found it easier to comfort my DSs like that and if they got a feed at the same time - hey, so what?
If you are feeling overloaded and over-analysing things, perhaps an earlier visit to your baby clinic to get an accurate view of weight gain would set your mind at rest. Although, bear in mind that sometimes they grow more in length one week rather than putting on the ounces, and that they don't necessarily put on weight in a linear fashion if BF.
WRT frequency of feeds, if you're offering a boob when she cries, then she should be getting what she needs. FWIW both of mine were on both breasts for about 10 minutes a shot, about 8 or 9 times a day at this stage - but I can't remember now if I was counting those 'comfort sucks' (don't think so). I don't know if that is any use to you as surely the size of the baby must make some difference, and both of mine were big lads (above the 50th centile).
WRT PND, I was as stressed out as you sound when my DS1 was 10 weeks. It exhausting, it is stressful - especially when you get complications, and - like you - I was soooo driven to continue that everyone around me must have thought I was little bit bonkers and losing the plot... But if that's how you feel, you can't help it. Don't lose sight of the fact that you've successfully raised 2 other kids (and I think you said that you BF them), and so you know 'it works'.
Is your partner broadly supportive of your attempts to EBF to 6mths? If so, does he know the strength of your convictions and have you discussed what he can be doing to help you and the other DCs?
Wishing you well.