Karen, is is possible that the chain on your flapper is too tight and allowing a small amount of water through? I didnt think so but worth a check, try this. If you lift up the flapper, theres a brass or plasitc “seat” that the flapper seals against. run your finger around the sealing edge with the flapper up and make sure it is smooth, no bumps etc.that could let water through, and remove your flapper and inspect that it is flat and supple. Somehow the leak is there 999% of the time. To see where the water is going, after the toilet has been left alone for a while, sprinkle some comet around in the bowl above the water and you’ll see the water coming down.