Hello Cecilia,
I am so sorry you are going through this. It is hard enough, symptom wise, and then to add the shock and confusion of having CD and not UC is tough.
I also spent 8 years as a "UC" gal. I actually had a proctocolectomy and a j-pouch. The j-pouch was always problematic, but last January I started to develop fistulae, which changed my diagnosis to CD.
I was very much in shock and confusion. I was also angry. My GI did say that a person with UC can also develop CD, so it wasn't necessarily erroneous all those 8 years.
I was on Remicade for my UC (before the surgery) and then started again in February. It was never super effective for me (after the first 6 months eight years ago) and it wasn't this time either. Hopefully you find it helpful though. I switched to Humira 6 weeks ago, and I will tell you that it has given me my life back.
Imuran is usually given (or 6MP) with the biologics. I found that by the time I had progressed to using biologics, Imuran wasn't worth taking as it gave me some yucky side effects. I felt nauseous, run down and sick. But that is just how my body reacted.
I wish you luck with the Remicade, and if you do not feel it is effective, do not let the doctors insist that you stick with it after maybe 6 months. You can always advance to Humira, which I find much easier and having less side effects.
Good luck.
~Tammy