Seriously, somethings not right with my range anymore. I switched from a 5c mouthpiece to a 3c mouth piece. There was a short period of glory when I could hit F above staff and hold it without dying, and my high E was solid. Now, I struggle with my range. It's crazy! With my 5c mouthpiece I didn't have such a problem of C above staff like I do now. Should I switch to 7c? I really need to be able to play high and bright notes again. I've been slurring like my teacher told me, pencil exercise, and petal tones but somehow I'm getting worse. I think my embrouchure is bad. So please, what am I doing wrong?