What Causes Mild Back Pain And Discomfort In Abdomen With Bleeding?

Am a lady of 42,i have one son aged 7;i had a perfect text book pregnancy. I came of my contraceptive pill after 2 yrs to have another child in may this yr,after two wks I had a period which lasted 3 days and was normal.i then intiicipated that all was well and calculated my ovulation and conception dates as 17th to 22nd june. This morning I started to bleed, red in colour slight clotting and enough to stain a pad brown in colour. I have mild back ache but have always had problems there, a little discomfort in abdomine other wise feel ok. I fear that if I have concieved that it has not attached.