I would recommend getting a stool test to check for possible pathogenic causes to your worsened symptoms (make sure there is no c diff lurking there which mirrors UC flares).
There's a percentage of us (20% feels about
right) that initially respond well to remicade and then begin loosing our response over time. The good news is that the remicade dosing is variable, and often increasing the frequency and/or dosage is enough to bring you back into response again (as you initially experienced). Some of us just need more medication than the initial amount given to sustain a response over the long-term. Typically they start us at 5mgs per kilogram every 8 weeks. They can do remicade every 8, 6, or 4 weeks. They can dose remicade at 10mgs per kilogram. So the maximum dosage for UC patients is 10mgs per kilogram every 4 weeks.
Depending on the gasteroenteroligy practice, they might increase your dosage experimentally to see if it helps or they might want to first test your Remicade/Infliximab serum trough (minimum) concentration and test your anti-remicade antibody levels. That test will tell you whether you have enough medication in your system just prior (within 48 hours) of getting your next remicade infusion. Your body might be using remicade up fast. Antibodies, if found, make remicade less effective and more medication can counter low levels of antibodies. You've failed remicade if you test with high/sufficient remicade levels with zero antibodies, yet are still experiencing awful UC symptoms. It's a good diagnositic test that gives you some answers on what exactly is going on (not essential but helpful). Prometheus laboratories in USA, California, invented the test (they call it Anser IFX) and still offers it at a premium. However, that test is now generic and available in many labs across the world for a better price.
/www.anserifx.com/how-it-works.aspx/www.labcorp.com/test-menu/29496/infliximab-concentration-and-anti-infliximab-antibody