Husband playing husband with his Ex Wife

I’m getting really annoyed with my husband playing husband with his ex-wife. She calls him asking for him to take her to the store every week. He says it’s for his daughters that they have together, but that doesn’t make sense. She lives just a couple of block from 2 different grocery stores. I’ve seen shopping carts on craigslist for $20, so it just doesn’t make any sense why he should have to take her. I would understand if he was taking his daughters, or if it was an emergency and she needed to go to the Dr. But she has even had him take her to her Dr. Apt. She had some kind of testing done (not that there’s anything wrong with her just preventative testing). She was put under, so when we went to go pick her up he told me that he might have to hold her up. Which really upset me. If I put him in the same situation with my ex husband he would have definitely had a problem with that! I’m just really getting frustrated. When I try to talk with him about it, he gets really REALLY defensive about his ex wife, which also really bothers me. I’m not sure if he just feels he needs to do her favors because he feels guilty, or worse if he still has feelings for her. If that’s so I wish he would just do me the favor and tell me that so I can stop wasting my life with someone that’s not putting me first.