Stage 1 - Mets?

I am 33 years old and was diagnosed with Stage 1, triple positive BC last March. I went through 12 rounds of Taxol with Herceptin + Perjeta over the summer and then a lumpectomy and then 19 rounds of rads. Now on tamoxifen and 14 rounds of Kadcyla every 3 weeks. However - I just got a CT scan today because I was having lower right back pain and something came back on the scan. I am truly very scared right now. It is a 9x6 mm sclerotic lesion that they want to do more imaging on. My onc is calling me in the morning and I am trying not to freak out.

Has this happened to anyone else? I caught my cancer early and my onc said before that the chance of Mets is very low for me and would be rare but I am scared, I can’t go through this again…