Should I be concerned?

My first post. I am 62 years old. I was diagnosed with PC back in Nov 2020. My PSA was 8.4. My biopsy showed the cancer was limited to the left side of the prostate. My Gleason was 3+4=7. The urologist stated the biopsy showed "unfavorable intermediate risk". In four of the sic biopsy samples perineural invasion was identified.

I elected EBRT (45 treatments) along with Lupron, 1 shot in Nov, 2nd shot in Feb, no further shots. My first post treatment PSA (after 7 weeks) was 0.6. Things were going well except for some of the Lupron side effects (night hot flashes and some weight gain).

Two Monday's ago (Aug 24) I noticed a discomfort around my tailbone. It felt more like pressure than anything. I let it go thinking it would go away but it hasn't. As of now, that appears to be the only place with any issue. Taking 2 Ibuprofen seems to help with the discomfort.

Reading online it seems likely that my cancer has metastasized to my bones but until an examination that's not definite. Anyone that has had PC metastasize to the bones, how did it start? Did it come on suddenly like myself? This has thrown me for a loop mentally. Reading about this online has brought on much anxiety though this site I seem to see more positive outlooks and results. I have an appointment with my urologist next Thursday and the oncologist is contacting me on Tuesday to set something up. Are there any good articles or such that I could read up on bone metastasis to calm my fears? Thank you all in advance for any help and support you send my way.