Running hurts my ribcage?

kikityme

So, I'm not a runner, I'll throw that out there right now.

I'm on day three of the c25k app. I understand the thigh pain, but what realllly hurts is the muscles around my rib cage right under my breasts.

My question, is it form? The bra I'm wearing? Breathing? A day off and the legs go back to normal, but the rib cage is just screaming at me to stop. I am fairly heavy chested (well, heavy all around, but especially "up top") but I'm wearing 3 sports bras, trust me, these things aren't moving.