Yeah, sadly we have to keep deworming pets on a monthly basis-- probably once a month is good. This is for maintenance. Vets will only say to do this once when they're pups-- and that's it for the life of the pet.
If you use herbal dewormers for pets- you can safely deworm them with these once a month.
As for your itchy ears- Ive had that also. Seems that alot of the time, if your bowels are constipated- the dewormer herbs drive some of the smaller thread worms to the upper parts of your body. Sometimes they may find themselves in your ear canals or sinuses.
what I do (besides regular colon cleansings) is get cue-tips and dip them in tea tree oil, or Neem oil but especially Oregano Oil!-- and stick that in the ear with a cuetip- it will kill them off. Do the same with your nose nostrils at night and in mornng also.
Also, keep the ear drums clean-- maybe use those ear candles. (I have to try those- I heard they work!)