New secondary: Pitch change... how to stop?

New secondary: Pitch change... how to stop? So the past few days I have noticed that my prolongations are taking a little longer and there is a definite pitch change at the end- I'm going high, I cant isolate it or replicate it enough to know whether I'm doing it or if its just happening spontaneously. But it happened like 25 times now and mostly on vowels and H- mainly "I". I typically prolong initial vowels but now I have noticed that just before I can move on to the next syllable, there is rather sharp pitch change at the end. I can hear it and its like a squeak, like when you try to sing in soprano and your voice breaks coz you weren't made to do that. Its like I run out of air but then the reserve kicks in but its making me squeak. I cant seem to stop this pitch change and have never had it before, or the running out of air. I always start at the top of a breath- ALWAYS. Dae know what this is and mainly how to stop it?