Adolfo, my darling man, there is absolutely nothing wrong with using a photo as a reference!! A very many great artists do it all the time. There will always be the kind of person who thinks of themselves as purists and who will poo poo this method - good luck to them I say!
What matters Adolfo is not where your reference starts from... it's what you do with it. I can guarantee that three people will start from a traced line drawing - one will make of mess of it, the other will do the bare minimum and leave it flat and soulless and the third will end up with a work of art that is totally original, individual and unique!
And you Adolfo are that third person! Your art is totally awe inspiring. I feel so proud and privileged to know you just one little bit.