Do I need more lip filler? I had .5 ml and can't see any difference. (photos)

I had .5 ml of Restylane 3 weeks ago in my top lip, I loved the results on day one but after the swelling had gone down I can't see any difference other than a fuller lip above my actual lips. My lips are not symmetrical naturally which I noticed more after having the filler. I've asked the doctor to put another .5 ml in but she said no and to wait for a few months. Why is this and if I do wait then should I get 1ml instead of .5 ml or will this then look unnatural? I've attached photos...