Why am I resentful and losing feelings for my fiancé?

When I lost my job we made an agreement that i wouldn't have to work and pay for my half of the rent if I stayed home with the girls while he was away so he wouldn't have to pay for childcare.

What happened instead is I am now his slave because I no longer pay $426 for rent. I am now a full time mother to 2 girls (note that I am not biologically or legally their parent) I wake the oldest one up for school, get her ready for school, make her school lunch (she's in kindergarten), walk her to the bus stop, I then go to school myself for an hour and 20 minutes then I come home and care for the youngest until the oldest gets home from school. They play for about 3 hours and then I bathe them and cook dinner for everyone. I get them out of the tub, dress them, and do their hair. We all sit down for dinner and when they are done they put their dishes in the sink and are put to bed. I tuck them in and depending on the time I will read a bedtime story. I then wash all the dishes then shower, get in bed, etc.

What is my fiancés roll?

Well he's asleep the whole time I'm caring for the eldest daughter. He eventually wakes up after I leave because the youngest is in the house with him. He'll either go to the gym for a little bit or just stay home and play his computer games. When I get home from school, he leaves for work for about 5-6 hours. Comes home and sits at the table playing his computer and tells me to bring him his food. When he's done eating he's sits there for a few more hours playing his game. He'll then shower and play the game in bed for a while. When he's finally done playing for the day, he will finally try to genuinely interact with me around midnight. Usually just seeking sex and when the deed is done, he passes out.

I am now wanting to return to work because he is constantly throwing in my face that he pays all the bill and he's the reason there's food in my belly and hot water on my back. I told him he needed to find childcare/ after school childcare soon before I start working again. (Note that I am a couple months behind on my personal bills because I've been watching his daughters) Since I told him to find childcare he accused me of threatening him and told me to "stop playing mom with the girls if I have one foot in and one foot out the door". When he said that I was extremely insulted because I literally do everything for them.

Questions you may be wondering?

Who's name is on the lease? Both of ours.

Who provides food? He has a EBT card.

How old are the girls? 3 & 5.

Where is the girls mom? In another state, being a "dead beat" as he always says.

How long have I been dating him? 5 months

How long have you been engaged? 3 months

How old is he? 25

How old am I? 21 as of last month

The million dollar question!! Why haven't I left yet?

I am someone that has an enormous heart. I am the daughter of a dead beat father, though I have an outstanding mother, I know how they feel. Growing up and even til this day I wish I had both parents. These girls do not have a mother and though their father is physically here, he is not the father he should/could be, in my eyes and I'm sure in the eyes of others. When I first met him I was skeptically. I noticed small things and swept them under the rug to find myself now stuck in the position I'm in now. I'm losing feelings for my fiancé and don't want to marry him anymore. I don't want him to be the father of my future child(ren). I don't want him to co-own 10 dogs with me. He is a very nasty(attitude) person. He is not happy with his life. He threatens me when I do wrong over the smallest things. He is selectively affectionate. He is not who he appeared to be when we first started dating.

Please, please, please, no hate. Constructive criticism is welcome, encouraging words, advice especially if you have been in the same position or know someone in the same position. I honestly already know what I should do, but I don't believe I can mentally do it without encourage from others.

Also I am by no means perfect myself.