Question about not knowing your fertile days ??

what are the chances of getting pregnant without pinp pointing ovulation an having sex when we feel like it could or could not be on my fertile days ?? .. ive been doing this for almost a year an nothing I had a m/c just a little over a year ago an using this method but we were having a lot more sex back then , could this be effectig my chances?? An any of you had this problem pinpointed the days an fell?? If so what method did you use to find your fertile days ??