Can I be pregnant ?

I am 11 days late could I be pregnant ? I was supposed to get my period on the 15 , I started to feel cramps so I thought I would get my period between the 7 days. Yesterday I went to the bathroom and when I wiped I had pink reddish spotting it , I thought it was my period so I put a tampon and when I took it out It barely had any blood it had a light brownish discharge and a few minutes later it stopped and the whole night nothing went down. I took 3 pregnancy test and all of them came out negative. Should I go get a blood pregnancy test ? Could I be pregnant ?