I knew my bf for about one year when I started living together with him. I had just graduated from school and he had just finished his house a few months prior to that. He was already living there on his own for the first time too and I usually spend the weekend with him but on school days I was at my parents home. When I finished school I had vaccation so I brought some stuff of mine over there (clothes, a matress etc) and pretty much didn't think it through just like you did your first time.
I never went back to my parents and we lived together. A year later we got married because we wanted to start a family.
I have no problem with people living together before marriage. It's a good way to learn to know each other very well. Living together is totally diffrent then dating or spending weekends together. The mistake I made was agreeing to marriage even though I knew he was totally wrong for me. He was my first real boyfriend and my first in almost everything and I just could not immagine leaving him. I wanted to believe he would change once we were married. You see it all the time here at the LL. People know their ex is no good, but they still want them back. It was something like that with my bf. only he was not an ex at the time, but he should have been. If only I had used my head and listened to my gut, and not listened to my heart. I was just scared to be alone. I was 24at the time. I shoud have left him and found someone better but I was young and stupid.
My advise... go ahead and live together, but if you see too many problems, don't take it any further. Getting married is a big step and you should be very sure you will be able to live with that same person for the rest of your live. Don't think they will change later, or change yourself for them. You must both be able to be YOU and still like to be with each other for a veeeeery long time.