Sorry to hear that you developed poison oak, and even more sorry to hear that it is on your face. Speaking from experience it can be miserable getting over poison ivy
(or poison oak). Poison oak, or toxicodendron pubescens (east coast)/diversilobum (west coast), causes a similar dermatologic response as does poison ivy. If you research it briefly online it describes the host response (meaning you in this case) as getting a contact dermatitis due to urushiol. Urushiol is an oily fluid that is made by the plant, and causes a significant cutaneous response in some mammals. The best protection is to avoid it all together (i.e. long sleeved shirts and pants if you know you will be working around it). More specifically it causes something called a type 4 hypersensivity reaction in most people. This is a cell mediated immune response which means that it takes longer to present itself then a more classic "allergic response" to say a bee sting or something like that. Unfortunately, it also means that it may be present longer for the same reason. It also means that antihistamines which work well in allergic responses do not usually have much yield here. Being that the rash is on your face and it seems to be getting worse, I would recommend making an appointment to see your general practitioner, or even a dermatologist
, to get checked out. They may decide to start you on a course of steroids. I hope this is helpful.