I would try to relax. This isn't much of a roller coaster - very shallow rises & dips. When measuring PSA down to +- .01 , I think psycologically, the variations look bigger than when measuring to +- .1 .
I think a +- .1 variation isn't something to worry too much about at this point. The overall trend is the important thing. There is always some "measurement noise". AND, you did go from a .13 to a .03 in only a month. Get another blood draw in 3 months. It might be back in the .05 range again. As long as it doesn't steadily rise, you are probably fine, I would think. Cancer doesn't take a holiday and then return home. Something else funny is going on. Good Luck.