As your both tubes are tied, then possibility of being pregnant is almost nil. There are several reasons of irregular period. These includes ovarian cyst
, pelvic infection
, hormonal imbalance, stress/ mental upset, uterine fibroid/ polyp, over wt/ rapid loss, irregular diet pattern, thyroid disturbance etc.
Here, you need to consult with gynecologist for relevant investigations after clinical examination like pelvic USG scan, hormone assay, thyroid profile, endometrial biopsy
following D & C, blood sugar & prolactin level etc. Proper treatment depends on etiology.
Take healthy diet with iron supplements
, control body wt, maintain genital hygiene. All the best.