Hitting a Training Plateau

Hey y'all - I am very new to this endurance training thing... I was a Division 1 basketball player in college, but needless to say, training to perform repeated 90ft sprints is quite different than any long-distance running. In the absence of a gym, I have decided to give running a try and (surprise) I love it! 

Anyway - I am now hitting a plateau in my training. For a week+ I have been crashing at the 3.5 mile mark (running ~8:00/miles). I'm currently running about 12-15 miles/week complimented by some self guided yoga and body weight exercises. Any advice for breaking through this barrier? My short term goal is a 10K, but I could easily see this growing into a passion that leads to marathons. All advice is welcome.