Q&A: Can I purchase over-the-counter progesterone cream?

There are many points that I want to make with my answer to your question.

1. Progesterone itself is classified as a thermogenic hormone. That is, it tends to raise your basal metabolic temperature by about one-half to one degree when it's secreted from an ovary that has successfully ovulated. It is secreted to adequate levels when there's been a decent ovulation. So treating low progesterone after a faulty ovulation is only wishful thinking. This won't help a bad egg. In the rare cases in which there's been an adequate ovulation but low progesterone, then progesterone will be useful to stabilize the implantation bed of the uterus for the fertilized egg. Repeated miscarriages may support this concern, but only a doctor trained for this can distinguish between the two.
2. The basal metabolic temperature is your resting temperature while at complete rest. Therefore, care must be taken to take it when you wake up before you do anything—even before going to the bathroom. Any activity will throw it off. Also, since subtle changes in temperature of less than a degree call for more exact measurements, you need a special thermometer, called a Basal Body Thermometer (BBT). A regular thermometer won't cut it. I still prefer the BBT even over the electronic thermometers.
3. Over-the-counter remedies aren't considered pharmaceutical-grade, and therefore, they're understudied, unregulated, and unreliable. For something as important as conception, physician supervision of FDA-approved and FDA-scrutinized hormones is necessary. Especially if there's a problem with ovulation.
4. Infertility can often be multifactorial (have many causes at the same time). Know what you''re dealing with before throwing good money at it. For instance, what if your husband has prostatitis? This could affect the sperm count, dooming you to continued infertility while you're paying through the nose for progesterone creams sold by people who usually have no biochemistry background at all.