5"30 is not a slow pace by any means. Thats impressive and more so if you have only been running a while.
Im simply too heavy to run at pace now but back when I was much lighter it took me a while to get my times down.
I don't think running is meant for us heavier guys.
I do a weekly 4-5km run/walk 'shuffle' with my dog at about 7"30 per km.