mess2k7ca

hi there i have a 92 pathfinder and when doing the timming belt i get everything lined up all the marks but the crank mark cuz i cant find it on the pan..when i go to turn iy over it will start but sounds like a tractor..then when i go to look at the belt again the marks are now like 4 teeth off every time i turn it over they move from the marks??/ do ya have any ideas i can try to get this running proper....