Doctor doesn't think this is ptosis, but rather a lack of an eyelid crease - advice? (photos)

I think you do have ptosis of your left upper lid. The lid crease is high, the margin Reflex distance is lower and your brow is higher on that side. I'm interested to see how the lid would react to a Neo Synepherine test. My guess is that it would assume a more normal position and the crease would normalize. I would get a second opinion from a fellowship trained oculoplastic surgeon

It is always difficult to make a diagnosis simply from the pictures. However, it appears that you have disinsertion of the levator, the muscle that holds the eyelid up and elevates it, from the tarsus, the cartilaginous plate near the border of the eyelid. This has caused ptosis. There is also caused your eyebrow to elevate trying to elevate your eyelid. You need to see a plastic or ophthalmic plastic Surgeon who specializes in treating upper eyelid ptosis.