Tamoxifen Fever?

I had a 1cm invasive ductal tumor removed in May; clean margins. I am having radiation shortly. I have been on tamoxifen for 6 weeks and at first I had hot flashes, but they've subsided. I have been running a fever though for at least a few weeks now, low grade around 99.6-100.1 or so. I have ruled out any type of infection with my internist. My questions are:

1. Anyone had this happen and does it subside with time? My onc has not seen this.

2. I also had the genomics oncotype test and it was a good outcome. How much am I helping myself with the tamoxifen anyway? Is this going to make a huge difference? My oncologist says "it improves your chances" and that's it; I am a statistician so that's not a great answer for me.

 Also, if there are posts about this on this website, please direct me, I haven't found them!! Thanks so much