Hi Carol, it sounds like you need to cover your starter a little more securely, so it doesn't dry out on the surface. The reason we say to "cover loosely" isn't because the starter needs airflow in order to ferment properly (it doesn't), but rather because fermentation gases can accumulate in a tightly lidded container and cause the lid to pop off. While cheesecloth or a towel can allow the gases to escape, they can also let in too much air, which can cause a crust or skin to develop on the surface of your starter. As long as your starter has room to double in your jar, with additional room for the fermentation gases to accumulate, it's fine to use a loose lid, or, alternatively, you can cover your container with plastic wrap (which will flex). 

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