Not Preggo But Trying

Hey everyone : )

i had a miscariage back in january
since then my periods went from 28 day cycle to 29-32 now my period is just scattered..... And its now hard for me to tell when im ovulating ( im going to start taking test soon and watching my temp )

anyways my last period was april 17th...... Im just not sure when im going to be fertile... Any idea's.

Thanks for the comments
rachel