How am I still so slow...

I did 15 miles this morning and ran 2. My average speed -14.5 mph.... UGH... How can I work so hard, feel so fast, and only average 14.5 mph?! My bike computer has to be malfunctioning... right? 4 weeks until Danskin.... My goal is to finish in the 1:30s, like 139:59 would be A-OK with me... Quick transitions and a fire under my butt are what will do it for me... I still have work to do.