Absent period. I do to get my period?

I took ipill in May and June. Periods came in both months. But in July I got one day period where i bleed just once. In August I got normal period. In Sept I was supposed to get my period on 18 Sept but it got delayed. I still(6 oct)  didn't get my period. I ran pregnancy test in homekit thrice on different dates and all were negative. I get breast pain. I even get cramps  when I jog or climb down stairs or even when i do nothing. I'm low in energy these days, I'm emotional and I also find it hard to concentrate. I'd also like to add I joined gym and started working out in Sept 1 onwards. I'm 88kg female with 5'6" height. I don't suffer from any disease or take any medication. Please tell me why my periods are so delayed and what should i do to get my period?