Late period

I recently got off birth control around November 2015. After taking birth control my period became very light. Now that I am no longer on birth control I still continue to have very light periods. I typically use light tampons and some days only a panty liner. On the rare occasion I will use a regular tampon for one day of my period. I have never had a history of irregular cycles, always regular and every month. My January period was normal starting after Day 27. My February period was irregular starting after Day 42. My March period was normal starting after Day 29. Currently I'm am still waiting on my period, meaning April passed with no period and I'm currently on Day 45. Should I be concerned? Why would my period become irregular after stopping birth control? I mean it's been over 6 months since I stopped.. Any advice would be helpful!