You absolutely can get pregnant right after your period. You can get pregnant any time of the month, before, after, or even during your period. Women just don't always ovulate when we "should."

Take a test if you're concerned. Rarely, tubal ligations can reverse themselves naturally, but it's not a common occurence.

Maybe it's possible that you are beginning to enter perimenopause and that can definitely change your cycle. My mom had a tubal ligation after my youngest sister was born, and she went thru perimenopause for almost 10 years before finally hitting menopause. She began perimenopause in her mid-30s as well.

I would take a test to rule out a pregnancy, and if the test is negative, probably you may be beginning to enter perimenopause. You can start having shorter or longer cycles, increased or decreased amount of flow as well as other symptoms.