Hi Kel

, welcome to the board ...
You are right to research PMDD if this is what you suspect you have. The knowledge you gain will help you when you go to see a doctor for an official diagnosis.
I suggest you take some time to read through the posts here on the board, there is some very good information here, as well as the links I have provided. My main web site "PMS & PMDD Information" (link above), will tell you all about symptoms, treatments, etc.
All the best, and let us know if you have any questions.
Anthea