Im 3 days late on my period but i had my tubes tied in may 2010 after my last child, is it possible they came untied and could be pregnant?

Yes, indeed!: Tubal ligations have a failure rate depending upon whether they were tied in one place or more, clipped, ringed, or cauterized(burned). Do a pregnancy test and if unclear see a MD if no period continues. When tubal ligations fail there is a much higher incidence of ectopic pregnancies.(pregnancy in the Fallopian tube), and they can rupture with massive hemorrhage.

Tubal ligation: A contraceptive failure after sterilization is a possibility. This is called reanastomosis when the ligated ends of the tube grow back together. Nowadays we use many other methods to ligate the tubes which are not actually "tying" the tubes. You can take a pregnancy test to rule out pregnancy.