Sounds to me like what you're experiencing is perfectly normal for someone your age. Everyone's voices change in different ways- there's no need to feel self-concious.
Some of my 18 year old classmates' voices have only just begun to change. Don't try and push your voice to be loud and tough- you can permanently damage your vocal cords by doing so, especially when your voice is changing. Just talk normally. If people make fun of you, don't listen to them, and don't let this pressure you into straining your voice. One day, the people who are mean to you will no longer be a part of your life. You only have one voice, however, so take care of it and make sure it lasts your lifetime!
Once again, try not to feel embarrased of your changing voice. This is a perfectly normal part of growing up. Soon enough, your voice will stabilize and it will sound much nicer. Just be patient, and remind yourself that pretty much every young man goes through what you are going through right now on their road to becoming a man.
It's not a bad idea to talk to your doctor. I'm sure that he/she can give you more information about the changes your voice will go through during puberty.
Best of luck!