What if your cycle comes on the feb 26 and mar 19 when will the next return.

Depends on your body: If you're very regular and always have 3 week cycles then you'd be on you're period this week. My guess is you're irregular in general. If this bothers you, make an appointment with a doc to start a birth control to make your menses more regular. If you're not bothered by having irregular menses then it's not a problem. Except that you can't predict them. Keep track of them for the next few months.