Converting Pregnancy "Weeks" to "Months"

So far I can say that I am "2 months pregnant" even though I can also say that I'm "12 weeks pregnant." But I thought 12 weeks equals 3 months, you say? Here is the best article/explanation I have been able to locate.

Also if you are interested, there is a calculator to see exactly when you or a preggers lady will hit the trimester milestones. Check it out here. If you would like to try it for our pregnancy, use April 17 as the ovulation date (you should see a Jan. 8 due date toward the bottom).