Sounds like perimenopause to me. Mine started in my late 30s. My usually regular, predictable cycles could no longer be counted upon. I would experience half a year of having my period every two months and then suddenly I was getting it every three weeks. My flow was different, and lasted for a shorter time. Everything was wonky for a few years, would normalize (somewhat) back to what I was used to, for another few years,and then get all wonky again. I was perimenopausal for about 11-12 years. Near the end, my period would come every three or four months, until it stopped altogether. After one year of no periods, I was officially in menopause at age 50.
If you're interested in managing perimenopause and menopause naturally, I highly recommend Susun Weed's book, The New Menopausal Years (revised version of her original Menopausal Years).