Please help - what is going on with my cycle?

On September 23rd me and my partner DTD I was due on my period on the 12 of October but instead a few days after my due date I started bleeding it was a very faint pink and only lasted two days, since the 12th of October I’ve done Pregnancy tests which have all came back negative.17 days late yest and I started bleeding this time with period pains and blood was bright red although not heavy this only lasted one day and has stopped already.

in august I took a tablet to stop my period whilst me and my partner took a holiday and as soon as I stopped taking it I came on for 8 days then I went 11 days without bleeding to another 8 days bleeding. This was before me and my partner DTD

i am wondering if the tablet I took to stop my period had just ruined my cycle or is there a chance I could be pregnant? But why would all 8 pregnancy test come back negative 

Ronnie