How to you get your relationship back to being positive?

My fiance & I have been together for 6yrs, have 1 child together & 1 not. Everything is A-okay until we moved close to his family ( I mean literally..2 blocks away) 5hrs away from where I'm from. I have no idea why, but I felt that his sister ( which is over 30yrs) & mother started attacking me by using my oldest child. Example... his sister came up to me & said with her mother right there, my mother doesn't like your kid...I was pregnant by the way with my youngest about to burst. I said nothing. But there has been plenty of comments similar, one day which was over a year & a half of keeping my mouth shut I blew up on the mother out of the blue...obviously she said something to trigger me. She got the whole family to think that I was the enemy. Of course they believed her b/c her daughter & herself said nothing around anyone, they wait til I'm there by myself so it's he said she said. UGG!!! Now I can barley stand them, I know it's a mutual feeling... but my fiance hasn't stuck up for me at all, on top of that he gets mad when I have something to say about his mom.... which is all the time b/c they live right down the street. My fiances parents expect him to stop over every morning before work, & he does... sometimes after, fine I have accepted thats his norm. They are in our face all the time, I feel that that's probably why our relationship is going down hill. On top of that he works for his father. All I want is to be happy with this man that I loved before we moved here. Since we moved here it's been complete mis trust &chaos all around.