Venting .....

I just don't understand. I have been ttc for baby 2 for two and a half years. I've done clomid for six months. I've lost weight about 21 lbs. Doc started me on Metformin in November. I have tried to reduce the stress in my life and have limited caffeine. I have done everything that I was told to do. I have dealt with the emotions of everyone around me getting pregnant. Now my SIL is pregnant and granted a part of me is happy because she has always had trouble and baby 2 has came so easily for her. But I'm dealing with anger and confusion. Because my SIL is pushing 400lbs does not take care of herself and refuses to listen to her doc or get her diabetes under control. I don't understand. I've followed my docs instructions. I weigh 248 and yes I know that's not great but I'm still working on it. But WHY can't I get pregnant?! I'm tired of feeling like a failure! I'm tired of people telling me to be happy with the one child I have. I am happy I wouldn't trade her for nothing. But I grew up an only child in the middle of nowhere and it was lonely. I'm tired of my hubby being mad at me because I'm so upset and he doesn't understand. He keeps telling me to deal with the cards that I was dealt. My question is when will I get the chance for a new hand? I'm sorry this is long and I'm sorry I'm just venting. But again as a child I feel alone and no longer have any strength for this .....