I'm sorry to hear that you had this issue! It sounds like you lost a great deal of blood, and I'm happy to hear that you are stable and that you got excellent treatment in the hospital to fix the acute problem.
Now, you will need to follow up with your OB GYN doctor
or your doctors
">primary care doctor to help you get to the bottom of why this bleeding occurred. One common cause of severe bleeding is a miscarriage, but it sounds like this is relatively unlikely in your case, since you had your tubes tied. However most doctors would probably check a pregnancy test, just to be sure, since there are very rare cases of a tubal ligation failing to prevent pregnancy.
Severe breakthrough bleeding is another possibility, although this is more common in younger patients and in those taking oral or injectable contraceptives (I assume you are not, given the tubal ligation).
Finally, it is important to rule out an anatomical problem causing the bleeding. For example, a uterine fibroid would be a common cause of vaginal bleeding, which can sometimes be severe. This and other similar problems would usually be picked up on an ultrasound, which is one of the tests your doctor may want to order at this point. Please speak with your doctor.