The progesterone only pills (POPs or mini pills) have to be taken VERY exactly for them to be effective. Too big of a risk for me personally. The on time window is about 30 min (as opposed to about 2 hours for regular pills).
Have you considered an IUD? Either the Mirena or the Copper version? Neither have estrogen. You CAN have an IUD if you haven't had a child too.
Mirena has progesterone only (fairly localized as well), known for shorter lighter periods (and sometimes none at all), good for 5 years
the Paraguard (copper) has no hormones at all, known for heavier longer periods and is good for 10 years.
Both have an adjustment period were irregular bleeding/spotting is normal (up to 6 months)
I have the Mirena (3 years in Feb) and LOVE it. I had spotting for about 6 weeks after I had it inserted. My periods got lighter right away and now I have no period most of the time, or just light spotting sometimes. My libido is like when I'm not on birth control with the Mirena.