I've been taking progesterone for several months now. My uterine fibroma (myoma) is still there. Why?

Switch treatment. Progesterone treatment for myoma is controversial. There is some evidence that Progesterone may actually even stimulate fibroid growth, contrary to anecdotal reports of treatment benefit by some clinicians. Ask your doctor about other treatments. Drugs that stop your ovaries from making estrogen & Progesterone have been shown to shrink, but not eradicate fibroids, for as long as you take them.
Don't go away. Progesterone is often given to reduce the heavy bleeding associated with fibroids. It does not make the fibroids go away.