Shortening the cycle/ovulation

Hi! I've read around a bit and saw that evening primrose oil can help shorten the cycle and maybe make it more regular. Important here is that this is stopped at ovulation because implantation can start afterwards and evening primrose oil is not for that. In my opinion you can only be sure about this by using ovulation tests? I find it very difficult to find these myself by feeling. Anyone here with experience with this?