Do Irregular Periods Cause Irregular Ovulation?

i have polsystic ovaries and i am trying to have a baby with my husband, i have had a period for the first time in 6 months and before that i caught my ovulation dates so we tried. Now i seem to not be ovulating have done the test on the dates i was supposed to but nothing and i have taken a pregnancy test which was negative. will i not ovulate regularly if my periods arent regular? And could i still be pregnant after having a period?