Verified answer

Practice, practice, practice. You also might want to think about putting some vasaline on the inside of your lips.

Really, your mouth needs time to adjust to the new structures that are in them, and it will learn as you continue to practice.

You have to relax your lips more on the low notes and tense them more on the high notes, and your mouth is pretty much affraid to do either at the moment.

Could be worse though, you could be playing trumpet with them,... ouch

Check your headjoint. Can you make a sound out of just that? You may have pushed the end stopper out a bit.