What am I doing to this relationship? What is this relationship doing to me?

We started off hot. Then we statred to have a lot of outside problems, and she was really needy, pushing things along, she'd fly into a rage and into dispair over issues related to my kids and my ex-wife, and I'd fly into a panic everytime she over-reacted. So I spend all my money fighting my ex wife for custody, and in the meantime we got engaged, but she feels more a minor part of my chaotic world than the center of mine or her own. We moved in with my mom, who became a total pain in the and acted superior. Then my kids refuse to see me as long as my fiance was around. Then we get us a new place to live away from my mother. Things got really tense. Then I told my kids that I wouldn't lose them over my fiance, that I'd leave her if it was the only way to keep my kids in my life. My fiance took my letter out of my hand and read it, and saw that part, and then she started being really cold to me for months, and only occionally made an effort or a sign of being kind to me or interested in me. We stopped having except every 2 weeks. I became irritable. Her kids were trashing our house, said didn't pay rent, even after gettign jobs (her son never did). I made an effort to be nice to her 4 to 5 year old son and have a relationship with him, but he saw me as competition for his mother's attention, which he momopolizes, spending all his time either acting out, climbing all over her, or biting, hitting and spittting her or her granddaughter. And my fiance has some sort of aversion to punishing him and lets him run amuck, throwing food and all sorts of things on the floor, when he doesn't get his way, or just to get attention. She spends all her time taking care of her son and her granddaughters. She has her son sleeping in the bed between us, about 26 days out of the 28 day month. Sometimes he falls asleep on the couch and it's Saturday night, and I think we are going to have for the first time in 2 weeks, and she goes right to sleep. We never spend time together doing anything. I try to take her out for a romantic evening and she brings her son and/or her freind and talks to them the whole night. I am ignored. I and ask if we can eat dinner together or do something together, and ask why we're not having nearly as often as we used to, and she says she is being smothered. I tell he I love her and she says "stop saying that all the time" She stops telling me that. I try to take her out to dinner and she dresses like she's doing yard work and insists on getting burgers at her favorite burger joint and going home. She loses her job. I Go away, and she neither seems like she is going to miss me when I leave, nor seems happy to seem me when I come back. She goes away and I take her to the airport, and tries to get out of the car and leave without kissign me goodbye or saying goodbye (I'd only been in town 3 days before she left town to see her sick father), and when she's almost ready to come home, I have to leave again. I make an elaborate "shrine" with love notes and cards we gave each other over the last 18 months since we met, and set it up in our room, so it is waiting for her when she comes home, while I'm still away. So we don't see each other for several days, and I come home and she doesn't even let me hug or kiss her at the airport, and spends the whole ride home on the phone with her daughter. Then a couple days later, I get really sick, and she starts to really mother me for a while, but then tries to say she wants to go out to the bar (where she never goes) without me because I am sick. When I try to call in sick, I go outside and close the door so her son won't come out and she lets him out and yells at me while I;m ont he phone and I yell back, and she freaks out and stops speakign to me for a week. I make he tell me what's going on and she tells me he doesn't know if she loves me. I leave for one night, then another. My friend tries fo give me a girl's number, I take it and text her, but then blow her off. We agree to work things out. She tells me she loves me. She calls me and when she can't get me, accuses me of cheating, finds out I changed my relationship status on facebook from engaged to sort of no comment, we fight, but we go away for the weekend we have one good day, but then I she picks up the phone, and says "no, yeah, he's here" and gets off, saying she lost signal. Then she starts texting, and goes out of her way to show me a text from her daughter, but it was 2 hours old. Then someone texts her an hour later, and she responds, and sees me looking, and quickly turns away, then gets up and goes into the bathroom to finish texting. then I look at her phone later and no texts and no calls saved at those times. Then I see that she's sleeping with her cell, and look and she's texting somebody in bed, and takes the phone fro