Not Ovulating?

I have been using ovulation tests for about 4 months now, I ovulated for sure the first 2 months but last month I kept getting faint lines but never a positive. This month I am not getting any lines at all not even faint & I only start testing durning my fertile window.. Anyone else have this problem or know what could be wrong? I recently started back at the gym and started taking Woman’s Ripped vitapak, Im not sure If that could have anything to do with it or not. Just looking for some advice. Been TTC 8 months.