The stuff which comes out a few minutes after eating/drinking something is stuff that's already been going through your bowels for a few hours - most likely the contents of the previous meal. Eating causes peristalsis - intestinal contractions - which in turns often prompts people to have a BM or, in your case, output from your stoma.
If you have gained weight, then malabsorption isn't an issue.
The fatigue I can't explain, I'm sorry. Does it vary at all? Is it worse or better in the first few days after the infusion, or worse/better as you get closer to your next infusion?
This is a bit of a long shot, but you aren't tapering off pred or have recently come off pred, have you? Steroid withdrawal can cause crazy fatigue if you have been on steroids for long enough to become steroid dependent. Also, what other meds are you on? There are many meds which can make you groggy or tired.
There is a possibility you could be dehydrated, so try upping your fluid intake, but not just plain water. Get some electrolytes in there as well. You can buy oral rehydration solutions from pharmacies, or google recipes online and make your own solution for pennies/cents. Or buy an overpriced sports drink or coconut water and add a quarter of a teaspoon of salt. I doubt that will solve your fatigue on its own, but it might give you a lift if you were dehydrated without realising it.
Finally, has your iron levels been tested? CBC should have covered that really, but just double check with your doctor that it has. Not just haemoglobin, but ferritin as well - ferritin is the marker for iron storage. You can have normal haemoglobin, but depleted iron stores. If so, you will need iron supplementation in the form of oral iron or an iron infusion to build them up again.
Get vit D checked out as well. And start taking a vit D supplement if that's low.
Good luck - I hope you can find an answer or a solution. Fatigue is one of the trickiest things to diagnose and treat, as it's a symptom of so many conditions :/
Dx Crohn's in June 2000. (Yay )
Tried: 5-ASAs, azathioprine, 6MP, Remicade, methotrexate, Humira, diets.
1st surgery 20/2/13 - subtotal colectomy with end ileostomy.
2nd surgery 10/7/15 - ileorectal anastomosis. Stoma reversed and ileum connected to the rectum.
Current status: Chronic flare. Do I have any other kind?
Current meds: 50mg 6MP; Entyvio (started 3/11/16)