Ever since I first got my periods they always came and gone like clock work. They lasted 5 days and…

Ever since I first got my periods they always came and gone like clock work. They lasted 5 days and there was about 28 days between each one. I got pregnant with my daughter Feb 2013 and gave birth to her Dec 2013. About 3 weeks after having her my periods started up and were once again normal. Oct 2014 I had my period and towards the end of November I was waiting for my period but nothing. December came and still nothing. I had taken multiple tests and all negative. February 2015 and still no period so I made and appointment with my OBGYN. They did blood tests and an internal ultrasound and said everything had come back normal. It has now been over a year since I have had a period. They went from being always on time and normal to not having any at all. I am ready to start trying to have another baby since my daughter will be two next month but it's kinda hard to when I'm not having any periods. Has anyone ever had anything similar happen to them?