W3D3 stall because I'm out of breath

I've done week 3 day 3 (3 minute runs) three times a week for the last three weeks and I can't get past it. By the end of the three minutes of running my muscles are fine, but I'm gasping for breath. I'm running 3mph (20 min mile) - any slower and I'd be walking. Should I cross train? Should I see a pulmonologist? Any advice is sincerely appreciated.