hi this certainly does sound like ammonia poisoning, i recommend a third to half tank
water change as i had this problem once, fish discrete ammonia which in turn turns to nitrite in which turns to nitrate (harmless to fish providing your
pH levels are under 7.0ph the ammonia then gets filtered, the filtration needs to build up good bacteria this can take several months you can buy bacteria building solution to hurry the process, never clean bacteria filter and only rinse in aquarium water you take out of the tank when you do water changes, it is recommended you get full test kit they should be ok in a few days or more.
goodluck
matt