"Hi. I am having a problem with my 3-year-old daughter. She's been potty training since she was 18 months with both progress and regression. She does very well at daycare with no accidents, but is having problems at home. As soon as I pick her up from daycare, she will poop in the car on the way home. Our biggest problem, however, is that she refuses to be changed without a huge fit. She screams at me while she's on the changing table and squirms the whole time. What advice can you offer? I have tried everything!"
No matter the reasons, though, this is her time. I would advise that rather than immediately loading her in the car and heading home at the end of her daycare day, you make sure she's gone to the bathroom before you leave. As soon as you come in the room, greet her lovingly and then shuffle her off to the bathroom. Take as much time as necessary and give her privacy if she needs it. This may mean locating another bathroom in the building if necessary since toddler bathrooms are often full of activity.
Hopefully that will be enough to eliminate that daily accident and thus the fight she puts up when she needs to get cleaned up and changed. You've said that she has no issues at daycare, so you know that she's capable. She's 3 years old and it sounds like she's mature enough to handle clean-up. Make sure that you're not doing all the work, but are assisting her when she has accidents. Keep your own attitude about the event in check so that she doesn't feel like this is anything other than a regular part of life and one of her responsibilities. If you express anger or negative emotion toward the accident, then she may be picking up on that and reacting to it with her own negativity.
If you've gotten control of your reaction and are treating this as casually as a cup of spilled milk, yet she still throws a fit, then feel free to institute a time out. First warn her that if she doesn't cooperate and start getting changed, she'll go to time out and then follow through if she continues to make things difficult. When she's done her time out, give her the chance to come back to the task at hand. Remember, she doesn't have to do it perfectly or happily (who enjoys cleaning up poop, after all?) but she does have to do it.
I can't stress enough about letting her take care of as much of the task as possible. She's got to learn to take care of herself and can't do that if you do things for her that she can do herself. If you're still putting her on the changing table, it's more like a diaper change for a baby than clean-up time for a toddler. Try helping her do everything in the bathroom while she's standing up instead. Offer her instruction, assistance and, most importantly, praise and encouragement. That way it's something that she's done for herself rather than something Mommy's done to or for her.