P.R.
It could be perimenopause. I started going into it in my early 30's with irregular periods and a lot of spotting for 1-2 weeks afterwards. My doctor did a bloodwork workup and discovered that my FSH levels were starting to rise (this hormone shows how hard the body is working to release an egg). I asked him if there was anything I could do, he said no.
I did research though and found that acupuncture (if done by someone with knowledge of women's fertility) can regulate your cycle and normalize FSH hormones levels - I've done it twice, at 35 and 39.
If you were trying to get pregnant and find alternative ways of normalizing your period and increase your chances, the book "Inconceivable: A Woman's Triumph over Despair and Statistics" - Paperback (Oct. 9, 2001) by Julia Indichova was my resource both times. It's a godsend.