<human>: Condense the text into a few key points

I live with my SO and have done for about 6 months now. last year, before we were living together, i lived alone and obviously found it way easy to control my diet and managed to lose about 10 pounds, quickly finding out that diet really IS everything.
However, now he's moved in, things have become more difficult for me. He's very skinny and conscious of being so, so tries to eat as much as he can and doesn't really care about where his calories come from either. This is a real challenge for me, not only with temptation, but with the fact that I feel some of the control has been taken away from me. If he wants pizza for dinner it's really hard for me to get up and make a stir fry for myself, not to mention that food shopping now feels like a his/hers affair which means spending twice as much money. I also cook for him most of the time which means cooking one meal for him and one for myself if I wanna watch my calories.
<bot>: moving in with my SO, who is consciously trying to gain weight by whatever means possible, has made it harder for me to watch my diet - any tips on doing so?