3mg might be suitable for some conditions, but for Crohn's and UC the recommended dose is 5mg. Even Remicade's official website says that. (Have to select gastroenterology under "Dosing and administration"). https://www.remicadehcp.com/ulcerative-colitis/dosing-administration.html
You need to fight this. You're being underdosed.
And no, I've never heard of Pred being used as pre-medication in the way that you described. I thought you meant taking it as a pre-med just before the infusion, which is commonly done to prevent adverse infusion reactions.