PSA is a very imprecise indicator, but while yours is increasing fast enough to worth looking into, it's by no means sky-high, and the time frame you mention seems pretty reasonable (just a couple of weeks until your MRI).

Let's hope the MRI on 28 Dec. doesn't show anything, or (failing that) that if it does, that a biopsy shows that it's either non-cancerous or very early and fully curable. The fact that the DRE didn't find anything isn't definitive, but it's another positive sign.

I know this is far easier said than done, but try not to let anticipation of the next test(s) ruin your holidays. Every holiday on this earth is precious, whatever your diagnosis ends up being. Hold the people you love close to you, laugh, sing, open gifts, and eat way too much food. Tomorrow will take care of itself. ❤️