is my body done?

Is it possible for your body to decide for you that it is finished with breastfeeding? My baby girl is almost 7.5 months and has been EBF. I have planned to breastfeed her until she was at least 1. She's always struggled to gain weight, but at her weight check yesterday, she actually stopped gaining weight. Her pediatrician wants me to try pumping to see if I'm still producing enough milk. Im going to do that later today, but now that she mentions it, I suspect that I'm not. Even though my girl is getting food now, I still make a point of keeping her breastfeeding schedule the same, so I'm not feeding her fewer times.
Can my body just be done? Are there any suggestions? Thank you!