Carbonation level increasing over time?

I kegged my ESB several weeks ago and dialed in a low carbonation level to keep it true to style. While it's not excessively carbonated now, it seems as if the level has increased. I just poured some and noticed some large bubbles along with the tiny ones. I typically leave the regulator in the neighborhood of 10 or below to dispense. The keg is kept in a Sanyo 4910, and I believe that the temperature fluctuates with the compressor cycling.

Is this normal? Or is it my imagination? ;-)

Yeh my sanyo is all over the place with its temperatures. and it is most definitely the cause for carbonation levels being all over the place. funny story about me and my sanyo just this week and a keg of stout.

sunday: keg of stout put in fridge at 40 to start carbonating.
monday morning: keg at 32 "i fiddle with knob and get the thing back to aroud 40-42
monday evening: keg up to high 40s "fiddle with nob again get back to around 40-42
tuesday morning: fine at around 40-41
tuesday evening: oven thermometer not reading. this means under 32 for me, i have some loose bottle in the fridge and they are not frozen so i figure all is well. so i go to take a sample from the keg and i get a drop then it stops WTF!!. so i open it up and i have 5 gallons of stout slush "this beer i then name STOUTY ICE". It was hard not to spoon out a bunch for a stout slushy also. so i fiddle with the knob again get the thing at proper temp and it then it held through today saturday around 40-42.

Needless to say i am sending payment out for a ranco on monday. this is one piece of equipment for me that is long over due

Ah, so my suspicion was correct...thanks. I guess that I should look into a temperature controller, too.