Hair thinning, shedding and patchy 2 years after hair transplant, 5000 grafts (photos)

I had a hair transplant 2years ago 5000grafts. For 18months, it was successful, and I was satisfied with the density. But recently, I have been shedding and now my hair is patchy. I am black African with coily hair, I don't smoke, I hope this is temporary and the hairs would grow back in density. Please help!