This happened to my husband too. He was sleeping in the recliner (abdominal muscles and incision still too sore to get easily in and out of bed). Many people on this board recommended the convex wafers which are doing a much better job for us than the flat standard.
Also Bill tries to eat as early as possible in the evening and then follows with beverages to thin out stool before he goes to bed. I should mention that at age 61, he gets up once a night anyway to use the bathroom so he just drains during the night as well.
Good luck and believe me, I know what you are going through. The best we have done so far is 3 days with a wafer and pouch.