Late positives/false negative??

Anyone had problems not getting positive pregnancy tests?? I’m on my 3rd round of clomid. I’m 15 dpo as of today and usually I start my period on 13-14 dpo like clockwork since taking clomid. I have endometriosis and PCOS so the pain is always excruciating and I KNOW when it’s coming. I haven’t had anything but super MILD cramps on and off that last like a minute or 2. Tonight I’ve been having some sharp pains on my right side. My boobs have been sore for over a week now and seems to be getting worse. They feel hard and heavy, and really sore to touch. ALL I’m getting is BFN’s. And I’ve taken multiple different tests. Any advice? I left a message for my doctor today but I was wondering if anyone else has had an experience like this.