Not sure how long you have plateaued, typically it need to be at least 4 weeks before you can concluded you have plateaued. Maybe it give 67 weeks.
You could stay at this level for a while, kind of reach a new set point, then make an effort to push to a lower %BF.
Change your routine is the only solution. What to change is the question.
In addition to the three choices
bkb33 offered, you could also.
Focus on increasing your muscular strength/size. More muscle with the same weight = lower %BF.
Once in a while I change weight lifting to a Tabata style.
I do this by rapidly moving with no rest between different weight machines. The only real rest is the time it takes me to walk to another machine. I use ~50-60% of my 1 rep max, do a quick 7-10 reps, move to the next machine, complete a full body work out, then go through that cycle again. Maybe only do 2-2 total sets.
My heart rate gets up to pretty high, and it seem to set my metabolism to a higher rate for a time afterwards.
Have you given thought as to your long term maintenance program?
If you do get down to less than 12% BF, I doubt you can maintain that for many years to come. I
think but am not sure that being very lean (or less than 13% BF) just isn't that natural and it's difficult to maintain as you age.
Very lean being under 18.5 BMI without really large muscle development. Because having large muscle will change how lean you really are even at a 18.5+ BMI.
Do you currently feel it is easy to maintain your 13% BF?