Im torn between my live-in bf and my ex i dont know what to do please help me?

me and my current BF have just moved in together. we had a long distance relationship and had decided a while back for me to get a job where he lives and move in with him and his family. its going ok but its a little awkward with his family and plus im still not sure of myself as it is such a huge step not only to move out of home in the country but to move 100 miles away to a city. but this isnt the bug problem. the big problem is my ex of 4 years who moved to New Zealand 3 months ago, we always remained close after we split (my bf is aware of this) and when me and my BF split up 2 months ago I said to my ex i would go over to nz to see him but now i cant because i have just moved in. my ex doesnt know about this current guy but rings me everyday begging me to come over and telling me hes made a huge mistake and wants me back and wants us to get engaged. i always had planned on marrying my ex i care alot for my ex and i dont know what to do i hate breaking his heart like this, please help i dont know what to do