Hi, zh. I somewhat know what you are experiencing, but want to speak to you about your constant questioning of self. I think it would be good for you to understand that to be an artist does not mean that you do well in school at all times, or in life at all times. Many wonderful artists stopped with school or avoided it in the first place. Teachers are just teachers - many are wonderful to some students, many are off in their own far away places. A mentor of mine who became a later colleague said he was always interested in the students who were not just facile.
My own last painting show was my poorest, in that I'd had eye trouble all that year I was painting and started to avoid painting for the show. I did finish, but I varnished some of the paintings too early, thus definition was lost. But I don't think I'm a bad painter - that was that year, and that realm of depression.
I'd like you to start liking and believing in yourself. Not all adults in superior positions are superior, we are all fragile human beings to some extent.
I don't have any idea where you live so I can't make any useful comments re your art community..