when does my hearing come back from an ear infection?

It is possible that the infection caused a lot of fluid to develop behind the eardrum.  Once the infection starts resolving, the fluid still needs to drain out before your hearing loses that "muffled" feeling that infections can cause.  This often happens rather suddenly and can be anywhere from 3-10 days after the antibiotic is begun.  Fluid either can rupture a tiny hole in the eardrum and drain as fluid/blood/pus out of your ear or you could find it on your pillow in the morning (less likely) (the hole usually then heals itself over with no long term consequences) or else drain out your Eustachian tube and down the back of your throat (most commonly) and you'll feel that "ears popped" sensation like on a plane or driving down a mountain.  If you get to 2 weeks and things haven't improved, please recheck with your doctor.  Sometimes the fluid needs decongestants like guaifenesin (robitussin in the US) or to be drained with a needle by a doctor.  Give it a little more time, I think you will be OK.

From your having to hold it open, I assume you have a severe external otitis, not an infection behind the eardrum.  Your hearing should improve as soon as the swelling goes down.  Remember the rule: "Nothing in your ear smaller than your elbow" Don't scratch at it.