How can I keep from having blowouts

[Coloquestions]

I am 3 or 4 weeks post surgery with a descending colostomy.  I cannot seem to keep the wafers, or barriers as some call them, attached.  The stool just pushes up and out and makes the wafer come off.  It does not drop in the bag like it is supposed to.  I am taking 400 mg of stool softner and miralax per day to try and soften things up as the doctor told me this should help the situation.  I have a recessed stoma, it does not poke out.  I have used concave and regular wafers, but not used the belt as I do not like it.  Any advice on how to make this work the way it is supposed to.  It seems to happen more when I am laying down, but has also happened when I am sitting up.  It is very frustrating.  I am having to change wafers every day due to leakage.