You're not a bad owner! I am in constant fear of mouth rot returning to LD and any time I see him re-align his jaw or open his mouth I have a heart attack. I would ditch the aspen and keep him on newspaper (printed or un-printed) or something similar so you are sure you haven't missed any potty-spots. I use Scott Shop Towels and although they are blue, I can always see right away if LD has made a mess. I'd give your vet a call and see what s/he says then go from there. Don't stress out too much, you are doing all you can.