I Have Been Constipated For The Past Week Now. I

I have been constipated for the past week now. I always have to go but it doesn't seem to come out. And the pressure is coming from my rectum, not my stomach. I've been drinking lots of water and eating prunes, strawberry, blueberry but i still feel constipated. I even took dulcorax supository and still feel it. I've done an ultrasound and everything seemed normal. What is wrong with me?