Hi my name is Jocelyn and I am one of the naturopaths at the Belly Belly centre in Melbourne.
I think there would be a definite link between your little ones constant teething and his ear infections. You must be the world expert by now on dealing with the teething!
If you are anywhere near the centre do bring him in as I am running a free infant's toddler session every Tuesday.
It sounds to me as if he definitely needs something to boost his immune system and some probiotics to help replace the ones knocked out by the antibiotics - there are some really good ones now for infants. Once their systems go out of balance after treatment with antibiotics it becomes a bit of a rollercoaster ride of one bug after another.
If you are not in Melbourne and want any further help just email me on jocelyn @bellybelly.com.au and I would be happy to send some things out to you.
Jocelyn King