Looking for advice please

I had been on the pill for 6 years and never had a period whilst on it. I stopped taking it about 2 weeks ago as TTC. Yesterday I got what I thought was a period but it only lasted the one day. Sorry for TMI but it was a brown colour and was stringy/ gooey. Was this a short period or what could this be? I am also experiencing cramps and back ache. Sorry if this seems a stupid question I am just abit unsure since it has been so long since I had a period