Remicade DOES eventually "wear off", but I don't think that means it has stopped working for you. Maybe you just need your infusions closer together than 8 weeks. I spent a period of time getting infusions every 4 weeks because that's how often I needed the remicade. Now I get it every 6 weeks. You shouldn't have to deal with the symptoms until the 8 weeks passes. Tell your doc you're getting symptoms sooner than 8 weeks. I think the remicade is taking longer to "work" because you're more symptomatic. Maybe you wouldn't have to deal with that if you were having the infusions every 5 or 6 weeks. Is your GI willing to step it up? That's what I would do.
eta: Tell your GI now. Don't wait till Oct. 3rd