I didn't start speaking until I was three years old and have stuttered since that age. I've heard a lot of experiences with people saying that they didn't learn to speak as well or as quickly as others and these people have/had stutters. My mum tells me that my older sister used to know what I wanted through my making gestures. Maybe this is because I found it hard to speak/realised that it was a lot of trouble. With your loss of knowing sign language however, as a student of English Language I can tell you that while kids can learn language very quickly, languages need to be spoken and practiced all the time to retain that fluency. And to answer your question, yes I think the fact that you used sign language so much contributed to you not being accustomed to stuttering. It depends on how often you used sign language though.