“Should I Go for the 4th Treatment?”

I've had three Fraxel treatments, and I'm contemplating if I should go for the fourth. It's $1300 for the entire face and $600 for the cheeks. Most of the deep scarring is in my cheeks. I've had a subtle improvement. I thought as deep as my doctor went, I would have seen a better improvment. I don't even see an improvment in my pore size. My first treatment was in Dec and it's now Feb and I don't see any new collagen growing. Can anyone that has had at least 3-4 treatment give me advise. Have you seen new collagen in the face? My scars are still very visible on my cheeks, it's so embarresing!