I have been with my fiancé for about a year and a half. He cares about no one but himself. He is a liar, cheater and a thief. He suckered me in his world and I believed everything he said. Left my home, that I can't go back to now, and I am stuck living with him. I have no help and now I am 9 months pregnant. I have no friends or family, he has isolated me completely. I don't know what to do to get out of here and be happy. Any advice?

First you get out, worry about being happy latter. Go to a shelter, talk to social services about what help is available to you

Explain please what brought this on?

Be strong, calm, and think about all the other options that you have got. You are now responsible not only for your life, but your precious baby as well.
Don't lose hope; yes, try to get help, I don't think staying with that guy will help anything. So, he is your fiancé right, great! Don't commit and merry him. Just leave him, look for help talk to a social service, I agree. Than try to get back in touch with your family if possible.
Don't let him talk you out of It, cheaters always try that, hopefully he will not though.
You can do it, don't give up, thank about your little baby, what a future he will have if you stay.

You should go to the authorities and if possible establish the fact that this guy is your fiancé and impregnated you. This guy needs to learn that he can not get away and should be responsible. You better take care of yourself and contact some social service and women organization who can help. Take care.

You have some good answers so far. First, I would see if there is a free legal aid group in your area. It needs to be proven that he is the father, so you can proceed with getting child support payments. I would also see about shelters, social services, and free legal advice.
Your Social Service Offices in your area would be able to help you with this, and suggest some others to see. I do wish you good luck.

You should go to the authorities

What do you mean by "authorities? This is not, at least not yet, a criminal matter.

To puffnstuff
Your best bet is to find a woman's support group that can recommend courses of action. They can provide a place to live while you get things sorted out. You may need to apply for public assistance. If you do they will probably require that you go after the father for support.

Legal aid societies general work with criminal issues, not civil.

If this is not criminal matter then what is it? A small fight? The guy isolated her? What is that mean? Authorities doesn't always means legal stuff in my understanding. Government runs many programmes for mothers and women, health programmes, medical programmes etc. and some non government organization also runs such stuff.