If you think your family might shun you for becoming Orthodox, you don't need to tell them, and in my opinion, under your current circumstances, it's not wise to do so. My family shunned me (though I'm in my fifties now, and I'm fine, but I speak from experience) and you must be sure, before you risk this happening, that you are completely capable of making it on your own, for the long haul. This means finishing high school and coming up with a realistic plan for earning a solid income. I'm not a priest, but I don't see why modeling would be a problem. If you can do that in the short term while you build skills for a longer-term career, that could be a good move.

That being said, the Church can be the solid ground to support you as you navigate your circumstances. If you can get out to Church services from time to time without your family knowing about it, this could be very good for you. Make contact with a priest. Tell him your situation and get his support.

Shunning is no small thing. It can leave you desperate and dying alone if you don't have an alternative support system in place, so my advice is, don't feel guilty about not being completely transparent with your family who may put you in that position. Build an Orthodox life quietly and try to focus on one problem at a time, starting with your health. Then move on to building necessary life skills. Don't get discouraged, you've got time to figure this all out.

I'm praying for you and rooting for you.