We're in the same boat, but possibly worse. DS is 7 months, and at his last check up we discovered he'd fallen way off the curve, and this was off of a curve that was already well below the 5 percentile range.
In the weeks following birth, he had gone from the 15th percentile down to below the 5th, but after that he chugged right along on that curve, and so the ped felt everything was okay. Note she has certification as a lactation consultant and has never once mentioned the word 'formula.' But this time he gained only 3 ounces in two months! She said we'd have to call it 'failure to thrive' at this point.
(He's thriving in every way except weight. He's super happy & social, meeting his developmental milestones, his height is in the 15th percentile, head circumference is somewhere between the 25th and 50th...)
Still, no mention of formula. Just advice to get as many calories into him as possible, to start introducing solids, and to come back in a month for a weight check. There was no way I was going to wait a month to find out if he was gaining - I went onto Amazon and bought a baby scale right away (the Health o meter for kids in case you're interested - I really like it!).
After he turned 6 months I'd given him a little banana and avocado on occasion just to gauge his interest level. At that time he didn't seem very interested and so I figured I'd wait a few more weeks. After this doctor visit, I tried the solid foods again, and he's really into them now. I've given him banana & avocado, carrot & apple puree, and today, sweet potato & broccoli blended with a little breast milk and butter. I mash some things and the rest I puree with my hand held immersion blender. I know the purees aren't very popular here, but I just want to feed my little guy in any way I can at this point, and it worked. I'll offer him finger foods soon as well.
We're breastfeeding more, not less now. I'm staying home and nursing through the day instead of taking him out for hikes or errands. (While I'll nurse in the car or in public, when we're out and about I find we go longer between feedings, and the feedings sometimes aren't as long.) About twice a day, in between nursing, I offer solids. They are in addition to the breast milk, not supplanting.
So far it seems to be working. At our appointment last Friday he weighed 11 pounds 7 ounces. Today he weighed 11 pounds 12 and a half ounces, so he's gained 5 and a half ounces in just a week.
By the way, as a baby I was also teeny tiny, only slightly heavier than DS at this age. And I was formula fed, so it wasn't an issue with milk supply. So I believe genetics really plays a role. He's so happy and healthy in every other respect, I'm not convinced there is a problem. But nonetheless, I feel like I need to get more calories into him just to be sure that he is able to do the growing he needs to do.
As for your concerns about the next visit, I recommend getting a baby scale. That way you'll be able to monitor whether whatever you decide to do, is having the effect you want it to have. I find it very reassuring. And there won't be any surprises at the doctor's office next time. We paid $70 something at Amazon for the one we got, but there was another highly rated scale for $50 something as well, if the money is a concern.
Though some here might disagree, just based on our experience, I suggest you continue to offer solids - your little one might not be ready this week, but this can change fast. And the solids can boost your LO's overall calorie intake if they supplement rather than replace breast milk, as illustrated by the graph on this page from Kellymom. Good luck! I'm sure everything is going to be fine.http://www.kellymom.com/nutrition/so...olids-how.html