My ds had ear infections about once every 10 days to 2 weeks from 3 months until his first set of grommets in at 20 months. He's since had repeat grommets at 3.6yo (after 8 ear drum perforations in 8 week) , and is due his third set next month age 6.6yo.
Speech wise, it did delay him, I think, if only because he had a huge language explosion just after his first set of grommets. He still has SALT to help with pronunciation, as there are some sounds he can't distinguish between. Mostly he caught up within a very short time. The main issue is concentration and behavioural at school when he can't hear, but that clears when he can hear.
I would go back to the GP and ask if they can refer you to ENT as he is not appearing to hear. Speech, they may not be worried about if he is in the "normal range" which is around 6-18 "appropriate sounds at 18 months, if I remember correctly.
But it does depend on your GP and your area whether they will refer you on. Some areas don't do grommets for children under 3yo. Some places have the bench mark of 8 ear infections before referral-which you will probably think is quite a lot, from my side, I wish ds had only had 8 
Did he appear to hear before the infections? Because there is also a possibility that it is a different issue than just glue ear.
I think it is uncommon for the parent to spot they're not hearing from glue ear, from my understanding. From my point of view, the problems were the infections, I didn't realise how little he could hear, as he adjusted, as a lot of children do, very well. He had this cute little habit of patting my cheek, which ENT pointed out was him turning my face so he could lip read. I thought it was just a cute habit.
So emphasising that he is not hearing, not responding to his name (ie developmentally behind) should increase the likelihood of being referred.
Hearing tests for that age can be very dodgy-I don't think we got an accurate test for ds until he was about 4yo. But they should be able to do an echo test, which, I think is specifically for glue ear. It should produce a graph with a peak in the middle. When there's glue ear, it is flat. But, as I said earlier, even a very poor reading may not result in anything being done at present, as they may prefer to watch and see.