Is my girlfriend going through menopause?

I've been going out with my girlfriend for about 13 months now. I am 25 and she has just turned 39. We have recently moved in together and over the last 3 or 4 months her drive has decreased to wanting it about once a week, if that. I have discussed my frustration with her and she is aware that we havent been having alot over the past few months. Most weeks it is twice a week but sometimes we can go for a week without her instigating anything. What worries me more is menopause. She is 39 so could be going through peri menopause? I never knew there was such a thing as pre menopause and it includes symptoms such as fatigue, reduced libido, dryness of the etc... I am worried. A friend suggested she could be pregnant. HELP!