Hmm Anne...it's possible his teeth are moving in his mouth. I know Riv seemed to have trouble a long time before any teeth showed. Try letting your bub gnaw on your finger, I did that with Riv, he seemed to suck when he needed comfort, but when he gnawed I knew his teeth were an issue.
Perhaps ask in the - is there a teething section? Otherwise maybe ask in the general baby section - of course, us September girls DO know everything but it would be fair to let others have an advice-giving turn if our suggestions don't work for you.

I didn't get a PM Sharle! Waaaaaaaah! (umm sweetie, you will know who is platinum/life cos they have an avatar!)