Hey Mike,
For immediate relief use- Milk of Magnesia
Since you are eating less you are going to have less or more infrequent BM's this is normal. or so doctor kowalski said.
But adding fiber into your diet will help also.
I usually drink at least one Special K protien Water everyday. It has 5 grams of protien and 5 grams of fiber. Extra protien yippi...
I also use Fiber Sure. one heaping teaspoon has 5 grams of fiber. Benefiber is also good but you actually get more bang for your buck with the Fiber Sure since Benefiber only has 3 grams of fiber in 2 teaspoons.
I put in a couple of heaping teaspoons of Fiber Sure. It mixes very well in warm or room temperature drinks once it is mixed in you can't taste it at all. If mixing in COLD drinks make sure you shake it real well. You can also put it in Soup and sauses.
WARNING THOUGH if you are just starting on fiber, your body needs to adjust to the extra fiber so may need some GasX for the first few days... ALSO start slow do not just go and add 30 grams of fiber to your diet the first day you will not be a happy camper. Start with 5 or 10 for a few days and Work up to it and let your body adjust or you will get the runs and very painful gas. NO FUN
You also must get in enough water when doing extra fiber.
SO I recommend putting a teaspoon in a 16 ounce bottle of water or whatever you want to drink. Do this a few times a day and you will get in your fiber and also get in your fluids.