My periods have always been regular but for the last 3 months my cycle has become very irregular. period been a week late. i am 36 years old?

Perimenopause: One common reason for irregular periods would be perimenopause. During this phase, menses becomes irregular as the ovaries become less functional. Complete menopause usually occurs in a few years, indicated by absence of menses for a year and usually accompanied by the other symptoms of menopause (hot flashes, etc.). Other medical conditions could also be causing this, so talk to your doctor.

Get checked!: Periods, frequency, intensity, regularity) all change over the course of your reproductive years, often with heavier bleeding & worse cramps as a woman ages (how unfair!). The first thing to check for when your period is late is pregnancy. Then if negative, other causes can be responsible, like thyroid hormone abnormalities, stress, poor nutrition, over-exercising, & sheer bad luck! See MD soon.

Ovulation: It sounds like you haven't ovulated lately, which becomes more common after age 35. Your physician can prescribe a progesterone to get you back on track. Pregnancy is another cause as is thyroid problems