Bawat, I am so sorry to hear about this. I do not understand the pain of losing your baby after having tried for so long, but i understand the feeling of loss. I miscarried in the middle of September. It was horrible and i felt all alone and that my friends and family could not understand any of it. For me its hard because my Mothers best friends daughter in law became pregnant at the same time as me and my fiance. She hates being pregnant and anytime i call she tells me how she wishes she wasn't. I don't know how many times i got off the phone to cry for an hour. The thing is that other people do not understand that small things like being over excited about their own pregnancy and tell you about it right now hurts more than anything else in the world.
That whole in your heart, and your hubbies, will not truly go away but the pain its causing right now will subside a little at a time. When your ob gives you the okay to try again, go for it! If you could do this once, you can do it again. And don't feel like a bad person, from my understanding not feeling happy for her will fade with some time also, but her actions should be addressed. Talk to your sister in law and explain the pain it can cause you when she talk about her pregnancy, but explain that you are happy for her and your brother.
sorry this is so long, God bless and many hugs.