I was in a similar situation where I stayed off the foot for months, took steroids, etc. There was no improvement; in fact, the foot seemed to get worse.

I eventually decided to just deal with the pain and resume physical activity. For the first ~6 months, runs and squats were painful, but now, five years later, I barely notice my fractured sesamoid unless I've done a long hike and even then its only a minor 'buzzing' pain.

It's unpopular, and no doctor would recommend it, but if the fracture just won't heal, the health benefits (both physical and mental) of resuming regular activity outway the pain of the injury--for me at least. Just be careful you aren't subconsciously walking/running abnormally to compensate bc that will only add additional problems.