MIL problems

MIL and I used to have a good relationship until I fell pregnant and she caused me a lot of upset and stress (long story). I cut contact with her as I don't need that during my pregnancy.

The problem is that she expects OH to be her handyman and do everything in her house for her when she demands. He has one day off a week and almost every week without fail she calls him demanding him to do something for her. Fitting shelves, moving furniture, taking her shopping, even changing the light bulbs. He obviously hasn't got the guts to say no as she's quite manipulative and will just cry if she doesn't get her way. His step dad has 3 days off a week and is more than capable of doing all of these things in his own house yet MIL is insistent on getting OH to do it whilst he's at work. She knows that's my only time with him and it's even more important now I'm pregnant and no longer at work. She keeps him round for as long as she can and makes sure he's exhausted before coming home so we can't do anything.

We arranged last week to go look around carpet right on his day off to plan getting carpets fitted in our new flat. OH just phoned me on his break at work to say he's going to move MIL's dolls houses around for her and fit a new toilet seat so we can't go look at carpets. I just wish he'd learn to say 'no, I've got plans can't your partner do it?'. It's really driving me up the walls and I feel like she's doing it on purpose. How should I approach OH about this?