Potty training regression with nearly 4 year old daughter

[amyapple]

My daughter, who is 3 now but will be 4 in about 3 months, has been having significant potty training regression over the past few months.  We started introducing her to the potty when she turned 2, although she wasn't terribly interested until she was about 2 1/2.  At that point, she would regularly go on the potty but was wearing pull-ups and still relying entirely on the pull-ups.  We figured that eventually she would start going less and less in the pull-ups and then we'd know that she was ready to move on to underwear.  That didn't happen, so when she was almost 3, we just moved to underwear during the day.  It was a bit rough for a few weeks, but she eventually got the hang of it.  She would still have accidents, but they became fewer and after a month or so there were some days with no accidents at all.  When she did have accidents, it was mostly at home, not at school.  She continued on in that way for a while and then a few months ago just started having more and more wetting accidents.  She knows exactly how to go to the potty and when she should go, but she just doesn't want to be bothered to stop whatever she is doing and she does not listen to what her body is telling her.  She is very good and using the potty for BMs, but just not when she has to pee.  She is fine most of the time at school, although has had more accidents at school lately as well.  She unfortunately just doesn't mind or even NOTICE being wet at all and isn't that concerned about it.  We've tried tracking progress on a calender and giving rewards, which worked very well for a while, but then she lost interest.  We now in theory do this, but she hasn't had an accident-free day in a month, so it's a bit pointless.  We keep re-setting the rewards, but it doesn't work.  We've also tried taking away some "reward" that she usually has, such as watching her favorite program on PBS every day, and only allowing her to watch it if she hasn't had any accidents.  She was upset at first, but now really doesn't care.  She's moved on to something else and doesn't really want to watch it.  I was very reluctant to do this, but we recently said that she can only sleep with her beloved "dolly" at night if she's had no accidents, but she just doesn't care.  She now had adjusted to sleeping without her dolly.  I've also tried just ignoring it altogether but that didn't work.

Any ideas on what else I can try?  Do think there could be a medical problem?