My playing suffered my senior year in high school as well. Maturity brought a change in my face. Like many people, my lips lost some of their fullness. I should have permanently downsized at that point, but I had no teacher nor anyone else to ask.
I don't think enough credence is given to a person's body changing during these years. Pull back, play softly, see if a different mouthpiece is warranted. Get used to your new face instead of trying to push it. Forcing things never ends well.