Darling - everyone from Leonardo da Vinci down has to have references. People spend years in art school drawing nudes from live models for heaven's sake. You have the gift - anyone can take a photo these days, but to pick up a pencil and draw well from one is beyond most people's abilities.
As for Leonardo - he spent years drawing virtually non-stop to get that good and practically invented anatomy illustration by dissecting bodies to find out how the body worked. He was a genius and may have had the advantage (and yes in his case it was one) of having a form of autism that allowed him to concentrate so hard on everything that interested him. Which was practically everything! He needed to have references to get that good and he still
used models even when he was an old man. It's all down to practice in the end - even the best people need to.