What Causes Blood In Split Despite Taking Celebrex And Folic Acid?

Hi I am waking of a morning with a horrible taste in my mouth, and go to the toilet and spit it is bloody not much but dark red. My medication is for Rheumatoid Arthritis One Plaqinium One 5ml Predisonale One Celebrex 30ml Methodrexinal 2 on a Friday and 2 folic acid Saturday I also give myself an injection Sunday of Enbrel,Could this bleeding be caused by medication I take tablets with a small bowl of cereal