I had my tubes tied back in 2011 after my 4th child... my periods have been regular... just this month I started spotting only when I wipe pinkish like mucus... my period is suppose to come by next week... could I be pregnant?

It's always possible. After next week, you'll be able to test. Those symptoms aren't necessarily pregnancy related though.

I would be very surprised with you getting pregnant after being sterilized. The human body is an amazing thing and I know that sometimes the tub tying doesn't work, but that is exceedingly rare.

How old are you?