Michelle's suggestion of using the Pearly computer/ basal body temp method is the absolute best, most natural method and despite rumors, does not depend on a regular period. Your temperature, if done consistently and correctly, tells you when you can and can not have sex safely.
I used it to get pregnant four times and used it ever since to not get pregnant. Six years.
I have a small paper chart on my nightstand. My alarm goes off at six am and I pop the digital thermometer under my tongue. It beeps. I put it on the nightstand and go back to sleep. After I get up, I turn it on to see the reading and put a dot on the graph and get ready for my day. When the dot rises, you know not to have sex. After three or four graphs, you can start to see your cyclical patterns. My left ovary begins a cycle that is 21 days long and my right ovary is 25 days long.
Within nine days after the start of my period, I can have sex freely. Luckily my periods are three days long. After that with condoms until day 17 when I can have sex freely again. The female condoms are preferrable. Or just abstain. There are worse things.
If your periods are extremely irregular, you should see a doctor. You could have polycystic ovary disease, ovarian cancer, hormonal imbalances or pituitary or thyroid issues.
Jennifer
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