I am 15 weeks pregnant, but am quite confused as to how many months along I am. There seems to be so many different ways to calculate a pregnancy, between lunar months and "real" months, that I'm not sure which is right.
Pregnancy lasts approximately 280 days, or ten lunar months (referring to a complete cycle of the moon which is 28 days). You actually become pregnant in the third week of your cycle. If your last period started 15 weeks ago, you are at the end of your third month, also known as the beginning of your second trimester.
Don't let lunar months throw you, lunar months last 28 days but most calendar months are longer so your pregnancy actually lasts nine calendar months. I hope this helps.