Tonsilitis

Hi , so on Saturday I took my son to the out of hours gp as was having a temp of 39-40 and was just genuinely unwell… I was told my son had an ear infection and his throat was completely clear. I was working yesterday and my mum had to take him to the doctors again.. he had been throwing up ever since he was put on amoxicillin so when she took him yesterday she said his tonsils were incredibly enlarged , a very sore throat and there is pus on his tonsils she said she didn’t understand how the doctor the other day missed this and called a doctor down to double check and agree with her (she was a pedatrician) and so would prescribe him penicillin…. I’ve found it really hard to even get him to take it but he had a dose and had been throwing up the whole night so this morning i contacted the doctors again and they said they’d prescribe him clarithomycin as they believe he’s allergic to penicillin & amoxicillin hence the sickness… I’ve just tried to get a dose into him of the new medicine and he is absolutely refusing to take it I even tried putting it in yoghurt and milk…. The doctor told my mum that he needs to be on an antibiotic he is too poorly to go without it and so now I’m at a loss on what to do… he kept gagging on the medicine and wouldn’t touch the yoghurt noir milk . Any advice would be appreciated.