Stabbing pain under ribs

Hello,

I've been running since last October and until the past month everything has been going great. Unfortunately i now seem to have developed a pain under the ribs on my right hand side.

I normally run 5km for two days, then one day off, with the ocassional 7km thrown in. The first time it happened i noticed a nagging pain, which gradually intensified, though i was still able to run. I don't recall having done anything the previous day that was likely to have pulled anything. I took a few days off, but when i went back to running, it still ached, and was bad enough on occassions that i had to stop running and walk home. Although the pain eased off when i stopped running, it quickly returned if i tried running a few steps.
I have tried taking a week off on two separate occassions, and although i haven't had to stop and walk since, i'm still definately aware of a slight nagging pain.

Any suggestions? I'm pretty sure it's not a stitch (it's higher than i normally get stitch pain, and somehow different). I have had a bit of a sniffle, though i can still breathe ok and don't seem to have any chest congestion...

help! It's really frustrating as i was hoping to up my distances.

Thanks for any advice in advance,
Anna