I surpassed puberty about 4 years ago. I’m fairly short and have stopped growing. My voice broke, but not completely. It’s been ranging from really deep to a little feminine sounding for quite some time now, and this is affecting my outlook.
You might want to visit a doctor just to make sure your vocal folds are healthy and properly developed. Once you are sure that everything is healthy and normal, the best possible thing would be if you could visit a speech therapist or voice teacher in person. If you have a health plan your physical doctor might even prescribe it for you and it could then be paid for.
Meanwhile, you might be able to help yourself by breathing deeply into your ribs and sustaining a gentle, low tone on the vowel “OH” almost like moaning. Touch your breastbone and notice if you can feel it vibrating. Once you can sustain this low “oh” sound, see if you can sort of “chant” sentences in this same place and with the same quality of sound. For example, “Hello my name is . . . I am from . . . My favorite book is . . . ” And so on. Be very gentle and do not force. Keep a strong, open body and just gradually remind your voice to sound in a lower, more open “OH” place. You also have to work slowly so that the strength can develop organically and you do not injure the vocal cords. Stop immediately if you feel any dryness, burning or fatigue.