Hunger strike

[TayKiren]

When ball pythons are on a hunger strike, is it normal for them to actually seem interested in the food, but just not eat it? My ball python hasn't eaten in around five months now. He's losing ~2.5% of his body weight a month. Nothing is too worrying, it's just getting to the point where I'm wondering if he's ever going to start eating again. When I offer the food, he tongue flicks a bunch and looks around for it like he did when he would eat regularly. However, he will get to the rat and then just.....sit there. He puts his nose right up against it, seems to consider it for a minute, then turns away and goes looking elsewhere. This is why I'm wondering if he's unhappy with something about the rat? The rats seem fine, nothing unusual...He ate the first couple of rats from the shipment I got, so I don't think it's something to do with a bad batch. It's definitely warm enough. I don't think it's lack of movement, as he never needed it before, and when I do it now he gets freaked out (I swear I'm not moving it that much). I tried cutting a hole in the stomach (as much as I could handle, anyway), and this did grab his attention enough for him to go over to it, buuuut then he just sat there again.

This latest feeding seemed the most promising in that he was more interested than usual, and he would look at me almost expectantly on the days leading up to it. But still nothing happened. Is this normal for a ball python on a typical hunger strike, or is he being picky? He ate Petsmart rats before I got him, which did smell more (which I assumed was a sign of inferior quality...). I'm thinking of buying some of those to see if that will get him eating again. Does this sound like a good idea? As far as I know, he has always eaten rats, so I don't want to go offering him mice or anything.

Thanks!

Edit: I realized I should mention he is an adult, 1755 grams and overweight to begin with. I took him to the vet a month ago since he needed a checkup anyway and was told he looked really good, had a good amount of flesh and muscle, and that if he is losing less than 10% of his body weight a month then he isn't worried. So, I'm not worried about his health.