Hi! i'm just wondering what could be the possible reason why i was bleeding but not actually on my period?

Irregular bleeding: Irregular bleeding can be caused by many things, some serious/some not: stress, weight gain/loss, new exercise regimen, lack of sleep, contraceptives, hormonal disruption, uterine fibroids/ endometriosis/ adenomyosis, ovarian problems. Typically the irregularities last only one or two cycles. If they continue or if the bleeding becomes very heavy, contact your Dr.