You would need to have IVF done or a tubal reversal. The tubal reversal is cheaper and is the better option I think. The failure rate of a tubal ligation is said to be 1-2/1000. Sometimes the tubes recanalize back together. If that happens it is a 50/50 chance that the pregnancy would ectopic, which could be dangerous. Although, it does appear that quite a few women have the tubes reconnect and go on to have a healthy pregnancy!
Unfortunately, with your tubes tied, there's no way for the egg to reach the uterus, so I think IVF would be the only option. Unless you get a reversal.
I am pretty certain that if your tubes are tied there is no chance of getting pregnant -