Take a glass of water. A sip works for me.
The angle of the trumpet should be determined by your jaw and teeth positions, nothing else. You need to keep pressure off of the top lip! Changing the position of your tongue should not change the angle of the trumpet!
Maybe PRACTICING the following could be useful:
in the circle of breath that I often post about we modify the following-swallow, inhale, exhale, and repeat. Once we have this down, we replace exhale with play. Build swallow into the breathing cycle - but placed at the correct time (the bottom of the circle), not in the middle of an inhale or immediately before playing.