Just to clarify, I don't take the 3-4 drops of oil each day, I swish with it. Now, I am also mixing that with 1 tablespoon of sunflower oil, and my oregano oil is not pure, it is diluted with olive oil already. I don't have many worries of overdosing with it at this rate. However, after my sinuses are finally clear, I will likely only use the oregano oil once or twice a week, perhaps a double swish on Saturdays.
I have always had respect for the strength of oregano oil which is one reason I have not used it internally until now. I've owned it for almost a year. I am taking a product called Candida Clear that contains oregano oil, but it all looks like powder to me. It contains 200mg with only 1.75% volatiles. So, the few drops I'm getting in my OP are probably helping add a bit more.