Teeth too soon

We have had a couple if grumpy days lately with my baby boy, he is normally so placid and happy but he is suffering with his little teeth. At just under 4 months he started getting really fussy, trying to chew everything and shouting and drooling a lot! I couldn't see anything on his gums but the signs were all there so in the end I got some teething gel for him. It was only when rubbing it on his guns I felt the tooth, right round the back at the bottom. 

Babies normally get the bottom front teeth first so it was really strange and explained him being out of character. I got granny to check and she confirmed it's a molar! A few people have said they think I should take him to the doctors as they have never heard if such a thing.

Does anybody have similar experiences? Does it mean anything? And what can I do to help him? The pain seems to last a couple of days, then ease off for a few days before coming back again. I have tried cooled teethers, calpol, baby neurogenic, teething gel... nothing seems to make much difference. He has had tears streaming down his face it's terrible, he seems to young for it all. A friend has suggested an amber anklet, any other tips?