I'm self-conscious about my voice, both speaking and singing. I'm in a very good men's choir, which I auditioned to get into, but I know that's just because I'm good at following instructions and listening to and mimicking other singers. I am not at all comfortable singing solo, which is a problem because a lot of people expect me to be a good/confident solo singer since I'm in this group. Also, I have a high forehead.
I'm a bass player, so I can sort of relate to what you're saying. What I've learned is that imitation of the masters or even simply those better than I am is what makes me a better musician. Something else I've learned is that you're your own worst critic. I hate soloing, even though jazz requires that all of the time. But then I talk to others who listened and think it was great. So I doubt you have anything to doubt about yourself. Having that concern about yourself is what'll drive you to being a better musician.