Food or teeth?

My DS is not quite 4.5 months old and I'm not sure if he's hungry or teething. We gave him a few spoonfulls of baby custard the day he was 4 months - not really wanting to start him on solids but more as a one off for a photo and some footage like we did for the other boys (they all ate solids regularly from around 5.5 - 6 months and were breastfed also). He loved it! No pushing it back out with his tongue like the other boys did - first mouthful went down then he grabbed the spoon for more. He had about 7 or 8 spoonfulls and would have kept going if we had let him.

For the last week he has been somewhat unsettled after a breastfeed. As soon as he finishes his fingers go straight into his mouth and he sucks and chews as though he's stlll hungry but he doesn't want more breastmilk (no matter how hard I try to convince him). He has also been drooling a lot more, but this may be because his fingers are constantly in his mouth :)

My question is - should I be offering more than breastmilk? His gums don't look swollen or red or anything. I just don't remember the other boys showing these 'hunger' signs but maybe he is ready.

What do you guys think?