Benxonatate Vrs Dextromethorphan

I have a script for Benzonatate, but ran out before I got in touch with my doc. I read it's not a narcodic like Dextromethorphan. So then why can I buy Dextromethorphan over the counter rather than a script. I was in a fire last May and my lungs still haven't cleared yet. Now I have a cold and I cough so much that people are starting to look funny at me. I only take the Benzo before going out as it works pretty well, it's easy to swallow, and it doesn't have any side effects for me except numish lips, like you just ate some cinnamon candy. I am also afraid of taking the Dextro because it says not to break in half, which I have to do in order to swallow it. And I don't want to become dependent on any drug mentally. Also it cost more than the script.