Is this a colostomy or ileostomy?
In my experiences, the mucus is always because I am not eating often enough so my body is taking what it can find. Have you had surgery recently? I have surgery last year, about 8 months ago, and by my understanding my body is still in over drive. My body is still grabbing everything it can to put out of me, even mucus because that's what it got used to.
If you are changing your wafers too often I would consider maybe a different eating routine or consulting a stoma nurse/ET nurse to see if your wafer is still right for you.
With the UTI, do you still have any symptoms? I would call your doctors office and get them to send another urine test requisition over to the lab and get it checked if you are worried about it.
Best of luck and I hope I understood your question correctly, if not, I have added this question to my watch list and I will repost when you comment and let me know otherwise.