I didn't see your actual situation. According to your description, there may be three reasons.

One is the protrusion of the upper and lower jaws, which makes your mouth look prominent.

The second is that it is possible that thick lips, hypertrophy of lip muscles or hypertrophy of mucosa make the mouth look prominent.

The third is that it is possible that your proportion is not harmonious and your cheeks are sunken.

But it is very likely that your speech is obvious, which is caused by the hypertrophy of your lips and the disharmony of your cheeks. You can ask a plastic surgeon to take a look at it for you.