help.. my ball python is driing me nuts (non feeding)

[seercirra]

so ive had him for 1 and 3/4 years, hes about that old too as i got him as a baby. he hasnt eaten for like 4 months, ive tried EVERYYYYYYYYYYTHING. as far as i can tell he has a perfect set up, and hes driving me mad.

hes just over 3 foot long and currently weighing almost a kilo, before his fasting he was just over a kilo, his enclosure is wood on 5 sides glass on the front, about 3 foot long by 1 and a bit deep/high. identical hides in each side, heat mats on both sides, (because its been so cold here his cold side was bottoming out too low, so i got another heat mat and thermostat just to make sure it doesnt go lower than 80/high 70's. his warm side is bang on 91.
i didnt trust the thermometers i was using, though that may be the problem (although both sides have a thermostat), so i brought a laser temperature gun. my temperatures were right all along, 80 cool, 91 hot.
hes using reptibark, has a water bowl he can bath in. i have a red light to provide decent background air temp of about 80.

before i try and feed him, i wave about a frozen mouse in his enclosure to see if hes interested, he usually comes out licking the air and heads towards the scent, showing interest. ok, so i assume hes interested, defrost the mouse/rat/wtfever (ive tried 2 types of mouse and rat, all of which he used to take), heat it up to a nice temperature by either hairdryer or warm water, put the mouse in - the snake behaves like it cannot identify it. it looks around the enclosure, like its looking for the mouse, but it WILL NOT take it, he behaves like its invisible. the mouse is definately warm enough, no differernt from how ive fed him since ive got him. im at a loss.

i know that bp's can fast for months, often it isnt a problem, but i am worried as its been 4, maybe 5 months now, and he does show interest (albeit alot less than he used to, he used to shake with excitement), but he cant seem to find it or identify it properly, else lacks the balls to BITE it. last night i put a mouse in there - he came out of his hide like he was looking for it, went right up to the mouse. and just sat there.. and then he spent hours circling around his enclosure doing nothing. even after i took the mouse out he was still circling around his enclosure for ages. its stressful to watch and i'd hate to feel he's starving, im really worried he'll just drop dead or something.

any help or advice would be much appreciated.