I think since you are in a perilous situation and your environment is not safe or supportive, give into their wish.
Your safety and health should come first, and since it seems quite impossible that theyll listen, go along with what they say.
Once you're independent of their influence, you can be yourself, but as long as you're dependent on them, I suggest don't enrage them too much
Also of you go along with my advice, don't do it suddenly, for then they'll think you're lying. Maybe over a week or even a month, act as if you are realizing that you're actually straight, act as of youre interested in the opposite s** and behave 'normally'
This might not be the way to prefer it to be, but it's the safest option given your situation.