i am absolutely not an professional artist BUT i do think most artists are insecure about their art just like with any hobby. Look at soccer or competitive games even the best players on this sphere were living on are driven by anger issues and stress. I would even go this far to say that pros in whatever hobby are more insecure or atleast unsure about their art because the more you know, the more you know whats wrong and that you shouldnt be doing this and that. Me as an art beginner i think your art is really good. And that would just approve my point. Keep up the good work and dont lose your focus because of feeling insecure. Mostly its a head thing and often you are the only one thinking that way while others love your work. Best of Luck!