I took robitussin p.m after drinking a glass of wine. could this cause damage to my body?

Avoid mixing: By now you have realized that it is generally not a good idea to mix alcohol with medications, even over the counter cough syrups. Robitussin contains guafenesin which is not a major problem. Depending on the type used, there are other medications -- including pseudephrine or benadryl. You can check the bottle. These medications can interact with wine, possibly increasing risk of aspirating.