All right here are a couple ideas.
I think it's probably the temps creating the pooping schedule.
You want a basking temp btwn 100-110 and you want that measured with a good thermometer, cheapest option is a digital thermometer with a probe, these are around $15 and any remotely respectable pet shop should have one. The stick ons, unfortunately, are notoriously inaccurate.
Beardies need these higher temps to aid in digestion. Because they are cold blooded, all their body functions depend upon them getting warm enough- it's like turning on your car engine, you gotta wait for it to heat up a bit before you blast the heat (or of course, you freeze yourself).
Your cool side needs to be in the upper 70s to low 80s.
The thermometer thing is super important as temps over 115 can actually hurt your beardie.
A 3.5 year old beardie only needs around 50 bugs a week, if he's eating more than this, let him go an extra day without bugs, the greens might get more appealing. One of my beardies is a belgian endive junkie and the other will eat just about anything orange; there's no accounting for their tastes! Try and switch it up a bit. This site might help with ideas
http://www.beautifuldragons.503xtreme.com/Nutrition.html
VERY VERY importantly! You need a different UVB. The 2.0 is not nearly strong enough. The plus side being, UVB lights expire after about 6 months, so you are due anyway.
What you want to buy is a reptisun 10.0 tube flourescent (like fish tank bulb). Not all UVBs are created equal, so definitely go for that one. The 2.0, 10.0, etc tells you the percentage of the bulb that is UVB as opposed to UVA or regular light. It is the best bulb on the market and around $20 online.
http://lllreptile.com/store/catalog/reptile-supplies/uvb-fluorescent-lights-mercury-vapor-bulbs/
UVB enables your beardie to process calcium, without adequate UVB their bones can be very frail. In severe cases it can result in metabolic bone disease which can cripple & even kill a beardie. Are you dusting crickets with calcium powder with D3? If so, what brand?
The baths are great! They'll often stimulate a bowel movement. You can try gently massaging his belly to help. Additionally, applesauce (no added sugar, etc.) kinda works as a beardie laxative. Or a small dose of olive oil can help lube things along.
I don't think that food is rotting in his tummy, but we can get him more active & happier with the above recommendations.
Good luck!
Kerry