HELP! Screaming toddler at bath time!

Hi I'm just wondering if any other parents struggle at bath time with their toddlers?
My 22 month old has never really enjoyed baths, even when she was really young she'd winge etc. And she HATES getting her hair washed. I've been told by our family doctor that she's got excma on her tummy so we changed from soap to soap-free ph-balanced bath wash, shampoo and bath oil about 2 months ago. Another factor is she freaks out when I dress her and put a shirt/dress on her. I try to do it really fast and try to make the shirt hole big so it doesn't touch her head but she crys a little bit everytime.
She goes through stages of liking the bath, then disliking it, but in the last three/four weeks she's been screaming as if I'm torchering when I give her a bath. Even just asking her if she wants to have a bath, she screams and runs away. She won't even sit in the water and play. We are on rain water too so is nice and chemical free etc. And we are landscaping our acreage at the moment so she plays outside a lot and gets very dirty then needs a bath, but if she doesn't go in the yard that day, I won't bath her cuz I just can't deal with it.
She absolutely loves swimming at the pool, beach, lagoon, dam, creek. We changed her bath wash ages ago, so that can't be an issue. I have tried to bath her in just plain water (no wash etc). I've tried to wash her in the bath, the laundry sink, my parents and in-laws, even in the little play pool outside. I've tried to give her showers, I've tried bathing her at lunch time, mid-arvy and the normal time (5/6pm). I've bathed her and not washed her hair several times to see if that made a difference. She has plenty of bath toys to play with and I try to make bath time fun and play games with her. I've made the water warmer and cooler, I've given her her dummy, I've tried to bath and shower with her, but everything I do doesn't help, she still losses the plot big time! I try to stay cool, calm and collected but then she keeps screaming even after her bath for about 15 long slow minutes. It sends me into a mental break down every night by that point and I don't need that as I'm pregnant.
I have no idea what could have triggered this as we did bath time at 5/6pm in the same bath every night. She didn't have a fall or anything that could have triggered it, she just started this faze and I need it to stop. I cringe at bath time and am avoiding bathing her if she's clean enough but that's pretty rare.
I'm after some DESPERATE HELP! Please if you have any ideas on how to stop this (none that I've already listed) or why this is happening, or if you've had an experience like this with your bub, please comment.
Thanks in advance.