Don’t want to overstep but one of the things that helps determine you have IBS over other conditions is lack of red flag symptoms. Being awoken in the middle of the night (as you mention) by your bowels, presumably due to pain or needing to go to the toilet, is a red flag symptoms and is suggestive that it isn’t IBS.

If it’s been checked out by a doctor then that’s fine but if not then might want to get it looked at :)