I have experienced over tone on E or D(First line and first space on staff) easily recently?

It seems if I elevate the clarinet, it will not be over toned?( but it may be over 45 degree if i do so)

So, how should I avoid over tone? is it my throat being too tight or tense will make it over tone?

take it to a shop and tell them to tune it up for you.
Some avice ihave for you is to always, always take your clarinet to a music shop to get it tuned before a concert, performance, audition, etc. that`s what i do.