perimenopause can start as early as 35, 40 being the average for it. it's the years leading up to menopause when the hormones start to fluctuate and you start experiencing symptoms. however, peri can last for 10 years or more before you reach menopause itself - menopause being that magic first year without a period, usually between 51-53.
peri probably has some relation to what you're feeling at the moment, but because of your history of depression and proneness to getting cheesed off anyway, it's probably a combination. like sara, i'd advise you to go and see your doctor. also do a bit of googling about perimenopause and menopause so that you understand a bit more about what happens and the potential symptoms you may experience...all 35 of them!