Reddit reviews Billings Method

It may have been an implantation that failed and was a miscarriage. This is apparently a lot more common than people realise with women attributing the odd bleed here and there to their periods being messed up. Take a pregnancy test to be sure. They are very accurate nowadays.

It's unlikely that a condom degraded from being in your wallet for a week after you bought it. They come with use by dates that are usually a couple of years.

And it still could be simply a weird bleed that some women have from time to time. Some women have very stable and predictable cycles but some women's cycles never really stabilise and odd bleeds happen from time to time.

Get your girlfriend to read The Billings Method: http://www.amazon.com/Billings-Method-Dr-Evelyn/dp/0345341112/ref=sr_1_1?s=books&ie=UTF8&qid=undefined&sr=1-1&keywords=The+Billings+Method.

This gives women an easy and natural way to track their fertility and ovulation by being aware of vaginal mucus secretions. You might want to combine using condoms and avoiding sex while she is ovulating to give you more peace of mind. You might both want to read the book, it's very educational about fertility and ovulation and women's cycles in general.

Don't stress out too much, bucko, welcome to wonderful world of adult responsibilities. It's not unusual for young people to have pregnancy scares from time to time but it sounds like you're doing everything right and acting very responsibly. Good luck with your future and look after each other.