I have an ear infefection but have finished my antibiotic and still cannot hear out of that ear. What could be causeing that?

Fluid behind eardrum. If you don't have fever or pain it is most likely from a resolving ear infection. It can take 2 to 6 weeks to clear up. If the problem persists see the doctor.
ET Dysfunction. Often times pain and pressure in the ear is caused by pressure from the sinuses - the eustachian tube. Even after antibiotics this can sometimes take time to open up. See your doctor to be sure, but they may suggest benadryl, (diphenhydramine) a decongestant, maybe a steroid nose spray....And unfortuately patience.
May Not Be Healed. The damage caused by the infection, may not yet have healed. There still may be fluid in your ear. See the doctor.