It is unlikely for your child to have lost height. Height may be lost in conditions that are serious in nature like spinal fractures
or lower limb pathology. Since he has recurrent ear infections, there are 2 possibilities. One that the infection has been inadequately treated or the ear infections have been due to a compromised immune symptom which would require a more thorough evaluation. Well a weight of 18 pounds is less for a 1 year old but not alarmingly low. Since he has suffered from infections, his nutrition should have been good to ensure he does not lose further weight.
Kindly get him re evaluated with an ENT specialist
for a careful ear examination.