A C12B cable I'm having problems

I am having an issue with the stitches being very tight when I cross the 6 stitches over the other 6. The previous rows are crossing over as well. It’s a pattern for bulky yarn.

Welcome to KnittingHelp!
A twelve stitch cable it a pretty large one and it [I]will[/I] pull the sts. You’re probably working on fairly large needles with the bulky yarn but the cable sts can still be tight and they will also pull the previous row’s sts. When you put 6sts onto a cable needle, don’t pull too tightly on the working yarn to work the next 6sts. Let the working yarn relax a bit and that may help.

Ok, I will try that, thanks.