I had unprotected sex on 18/8 night, he did not ejaculate in me. My last period had ended on14/8. I took iPill on 21/8 morning. On 29/8, I  had spotting and bleeding. Also abdominal pain and pain in thighs, just like periods. Discharge and blood is not much, but almost as much as 5th day of period. It is dark brown and somewhat thick. I took a pregnancy test twice, on 25/8 and 30/8 morning. Both negative. Is there anything to worry about? When can I expect my next period? After a month from last cycle or a month from this discharge?