Make sure your doctor is using the WHO chart, not the CDC chart. On the who chart, a BF baby shouldn't drop too many percentiles because the chart itself is based on how breastfed babies initially gain weight fast and then slow down.
But if your doctor is using the CDC hart, it may have shown your baby at a higher percentage initially (because bf babies gain faster) and now may show your baby at a lower percentile (because bf babies slow down around now), so her true curve may just be somewhere in the middle.
All that is a long way of saying that 10th percentile alone wouldn't worry me at all. But I would probably ask for a weight check and growth check before the 9 month visit, just to assess at the midpoint, since the percentile fell so drastically in the last two months. That way, I would be able to see whether she stabilized at 10 percentile, or continued to decline (which would only then potentially be cause for concern).
There have to be babies at 10% of the growth chart, and it doesn't have to mean something's wrong. It sounds like she's just a small, beautiful, perfectly happy little girl. We also are still feeding every 2.5-3 hours during the day, about 4.5 oz each time.
Haven't read all the previous posts, but you are a wonderful mother. Being a mom is hard, and she is happy, loved, and you take AMAZING care of her. As for her size, don't beat yourself up about it. I was a very small baby. I weighed 18 lbs when I was 1 year, and I am perfect (hehe). Every child is different. Hugs to you! Cheer up, you're awesome.
Re: Feeling down after 6 month appt
*hugs*
you're doing excellent, mama!