Hi Rita,
Your hormones are probably flucuating (and this may be the first of your skipped periods in perimenopause).
I am 49 (began skipping periods 6 years ago, and began noticing more peri symptoms in last year or so). I also have always had a high libido and notice now that there are days that I want nothing to do with sex and other days when it is all I can think about. I blame it on my hormone levels.
I am also very stressed lately (financial issues, children issues, yadda yadda....) and have had bouts of depression, which I know affect my sex drive too. Sometimes, I just need a little push in the right direction. We all have our sexual triggers (emotional, physical) and I would suggest focusing on them. That usually gets me going, even though I may think I am not in the mood.

I really think that what you are experiencing is transitory...(think positive girlfriend!!!)
beth