Light And Infrequent Menses After Oral Contraception. Why ?

i have been a mother of 1 child for 3 years now and i used oral contraceptive for two years until i stopped 6 months ago, since then I ve been having light and infrequent menses, the past two consecutive months, my blood won t discharge unless i pee..this lasts for almost 2 weeks.it never becomes heavy. it s use\ally dark red to brown in color. my husband uses condom when we have sex and i am very particular with hygiene so what seem to be my problem is surely not some kind of sexually transmitted disease right?so what is it doc? and also my menses comes exactly the right time it should be, 28-30 days cycle. i am 24