I have a cat who is roughly around 6 years old. He's an american short hair named Mr. Darcy, and he's normally rather skittish in disposition (I think he was abused before I adopted him), but in the last month, he's decided to stop using his litterbox.

The first time, he defecated on the mat right in front of my front door (and right in front of my mother--he actually made eye contact with her while he did it). We washed the mat, and watched him carefully. Soon afterwards, he did it again. After several BMs being left in the general vicinity of that mat, he started urinating (not marking; he left puddles on the floor, not the wall) in that same area. He's gone on the rug as well as around it. I blocked off the area, putting boxes and large things in the corners, taking the mat out of the room, and buying a motion detector which beeps at him and lets out a puff of air if he goes over there. He was scared by this device twice when he was about to poop over there, and so he stopped using that area. Note: The device didn't scare him while going.

If I put him in the litter pan, he will use it, and then beg me for treats (because the second time he BMed on the rug, I put him in the litter pan, and once he used it I gave him a lot of treats and praised him heavily. Now he's spoiled ).

However, after about a week of using the litterpan, he's started urinating and defecating on the rug and floor in the upstairs bathroom (which is rather random considering it's pretty far from the front door). My sister suggested a UTI, but he hasn't had any blood in the urine, frequent bathroom breaks, or straining. I did notice one incident in which he yowled while urinating, but that was several days ago in the backyard (I had let him out to burn some energy, though he is an indoor cat), and I think he was simply showing off. I have two other female cats who were nearby as he did it. He didn't yowl again after that, and there was no straining while he urinated then or in the next few days.

I took him for a vet visit before he started going in the bathroom, and he wasn't running a fever. He didn't have any abnormal symptoms, actually. The doctor did discover a heart murmur, but said it wasn't related, and I'll soon have him screened for that. The vet suggested anxiety and recommended "Feliway", a pheromone releasing device which sends a message to your cat similar to the one he or she will leave for themselves when they rub their mouths/face on an object. What they're doing is leaving pheromones to tell them that area is safe, and Feliway does the same thing, but it releases them into the air around the area they've been marking.

I guess it may be possible there's been some kind of trauma that has scared him out of using the litterpan, but if that's true, then I think he wouldn't want to use it when I put him back into the pan.

My best guess is anxiety. By the way, I haven't noticed any abnormal amounts of stress--in fact, he's been rather sweeter lately than usual. He hasn't run when I've approached him, which is an improvement (although he only does run about 25% of the time).

I have no idea how to solve this problem. The Feliway package recommends use for 90 days for best results, but I'm hoping I can fix the problem before then.

I'm going on vacation for a few days soon, and I don't think I can leave him here without locking him downstairs...

Any suggestions?? I would very much appreciate some help.
Thanks very much!