So wanting can be expressed just with "am"?
It can be in this instance. When it's used like this it's usually because you want or don't want to do something. I.E if somebody is talking whilst the telly is on you might say "Dwi am wrando ar hyn" (I want/am going to listen to this.)
is ' I'm not taking a picture' wrong? I don't see why it's not accepted.
I don't either. I was going to comment on this. I don't understand why this sentence is talking about the future.