Unlike estrogen, androgen levels don't suddenly drop when you reach natural menopause. Instead, androgen production begins slowly falling in your twenties. By the time you reach menopause, you're producing about half as much as you made at puberty. However, your ovaries may still continue to produce small amounts of androgens even after menopause. Some studies show menopausal ovaries continue to produce testosterone; other studies show they do not. One thing is for sure: if your ovaries are removed or damaged, you will go into surgical or early menopause. Some women who experience surgical menopause report a drop in sexual desire and drive.
This is a common problem with pellets. If you go looking for forums on the matter, you will see that it is rather typical for patients to have a similar response somewhere around the 4th and 5th implantation. This stems from poor oversight/management, and design flaws in the pellets themselves. Keep in mind that all pellets are made the same way. This may seem beneficial at first glance, however, what this really means is that “6 months” worth of medication dissolves in a way that sends your levels far too high in the first month, and then plummeting far too fast and low in the next 2-3.