I moved your thread here to our Options and Alternatives forum where other women have tried options such as Norethisterone and where there are many ladies trying to determine what is best with regard to their fibroids. You should find a lot of support here!
Norethisterone is a synthetic progestin so is not actually progesterone. The body doesn't quite process the two the same and women tend to have more side effects from progestin. However, both can be a treatment option for fibroids as estrogen is thought to promote their growth.
Fibroids can appear suddenly or it may have been missed on a prior ultrasound. Ultrasounds are not infallible tests. It could very well be that the hormonal issues leading to your bleeding issues has also caused the growth of the fibroid, or the fibroid is actually the cause of your bleeding concerns.
We do have a lot of information about fibroids in our Resource Database. You can find an option for Link Direction under the purple Information tab at the upper right of the screen. If you click on the purple Articles tab and choose Options, you will also find a few articles about fibroids.
To get you started, try this fact sheet:
http://www.womenshealth.gov/publicat...e-fibroids.cfm
Don't hesitate to post any of your questions here, but also talk to your doctor and seek a second opinion.