Could Injury To Chest And Abdomen Be The Cause For Dark Coloured Bowels?

My horse`s rear end rammed into my chest and abdomen -knocking me to the ground- landed on my back hitting my head being knocked out briefly -some bruising on chest - pain seemed to worsen as days went on . Its been about two weeks since the injury- and two days ago I started having black tarry stools . Passed out in the shower and several other times- and I am very week- blood count is 8- I am diabetic and on metformin. Can you please advise me. Could my injury of two weeks ago just now be causing black tarry stools?