Possibility of a healthy pregnancy after 4 years of having tubal ligation? i heard (even from dr's and nurses), its highly possible.

Less than 1%: Tubal ligation is considered permanent sterilization and theoretically has less than a 1% chance of pregnancy thereafter (since that was the goal of the ligation). Options for conception, therefore, include tubal "reversal" and ivf (which bypasses the blocked tubes). If a woman does conceive on her own after a ligation, there's an increased risk of tubal pregnancy.