Thanks for your query.
If you are not sure about pregnancy
, please take a pregnancy test.
meanwhile, slightly altered bleeding or spotting is common after tubal ligation
An ectopic pregnancy might be possible.
You have not mentioned your age, you could be going through age related transition phase.
Also, endometrial hyperplasia
etc could be a reason.
Please consult a gynecologist for internal examination and ultrasound
if the pregnancy test is negative.