This is just a 5-week-old pouch, so some adjustment is expected. That being said, there are some things that might help:
1) Stop eating around 4 hours before bedtime.
2) Try some soluble fiber (e.g. Metamucil or Konsyl) with dinner (and maybe with breakfast, too)
3) Try a *small* fatty meal (e.g. a spoonful of peanut butter) at bedtime.
4) Make sure to fully empty your pouch at bedtime.
5) Try Imodium or Lomotil at bedtime. Lomotil works a bit better for me, but it requires a prescription.
Good luck!