Lower back pain while running after lean mass gain!?

I've put 20lbs on this last cycle.  I used to do 7:30 splits on my 5k.   I started focusing less on cardio and more on lifting.  Now when i try to run I get lower back pain that all but cripples me after about a mile.  also i'm getting some calf and shin pain. 

i use custom orthotics and proper footwear being in the orthopedic shoe business.  the only thing i can think of is all the weight i've gained.  what can i do to get my running ability back!?  will i have to lose some of this mass to be comfortable?!