What Causes Irregular Periods After Having Stillbirth?

I had a stillbirth baby about 3 1/2 months ago. It was full term and they say it was a cord accident. I got my first period abot 8 weeks later and now 7 weeks later i still have not gotten it again. i was always pretty regular so i am wndering if this is normal and it always takes so long for the body to get back on track. thanks