Have you tried the regular laxative slurry protocol yet? A month is too long now, and I'd say there is definitely some type of impaction going on that needs relieved.
The best impaction slurry that I actually used myself to pass my rescue boy's 3 month long impaction of mealworm shells and wood chips is a combination of prune baby food, plain raw canned pumpkin, and unflavored Pedialyte. You can also add a pinch of Psyllium Husk, which comes in bottles of capsules you can buy at Walmart or any drugstore, it's usually labeled as "Daily Fiber" and it's just pure, natural Psyllium Husk, you empty a capsule out and put a pinch into the slurry. It works typically within 24 hours or less to pass the impaction.
If you empty a jar of prune baby food into a microwave-safe container, then add 2-3 tablespoons of the plain, canned pumpkin (the kind you find in the canned veggie aisle, that has no spices or anything else added but raw, plain pumpkin), and mix that up very well. Then if you're going to use the Psyllium Husk you add a pinch of it into the baby food and the pumpkin and mix it up very well. Then add enough unflavored Pedialyte to get the mix thin enough to be used in an oral syringe. Then microwave the mixture for a minute, mix it again very, very well, and check the temperature, you want it pretty warm, but not hot. I recommend testing it on your wrist, just like you would a baby's bottle. Once it's ready and you fill your oral syringe, you can try dripping it on his snout to see if he'll lick it off, you're trying to get between 1-2ml in him at a time, so if you have to use the method of putting the tip of the oral syringe under his upper lip on the side of his mouth, back towards his ear, then gently slide the tip of the syringe up his mouth towards the tip of his snout, all the time keeping the tip of the syringe under his upper lip. Once the tip of the syringe reaches the tip of his snout, he will automatically open his mouth. Make sure you have your thumb on the plunger of the syringe while you're sliding it up towards his snout, so that you're ready to push a small amount of the laxative slurry into his mouth when he opens it. Don't push too much of the slurry into his mouth at once, you don't want him to aspirate it into his lungs. Give him time to swallow it, then start over again by putting the tip of the syringe under his upper lip on the side of his mouth, back towards his ear. Keep repeating until you get between 1-2ml in him. Then put him on his basking spot for at least an hour or two.
After he basks for an hour or two you can try a warmer than average
bath. If you've added the Psyllium Husk he may poop during the first
bath, but it typically takes another feeding of the laxative slurry and then another warm
bath. I'd try to give him two feedings of this a day, so if you give him one tonight and then one tomorrow morning after his lights have been on for at least an hour or two, then let him bask for another hour or two, then put him in a warmer than average
bath, he should go.
Giving him gentle tummy rubs while his tummy and vent is submerged in the warm water can also help. Start under his right armpit with your finger and very gently rub in circles under his right armpit, and continue the whole way down the right side of his tummy, then continue to move inward towards his vent. Also, try to encourage him to swim while in the warm
bath by moving him around in the water passively and then seeing if he'll start swimming on his own. Typically the more they swim around in the warm water, moving their back legs, the better chance they will poop.