This sounds really tough, and loss of appetite at 12 weeks is definitely something worth flagging with your gynae or PD because they can check if there's anything contributing to it like hyperemesis or low iron levels. In the meantime, try focusing on smaller, frequent snacks throughout the day rather than full meals, and pick foods that are nutrient-dense even in tiny amounts like peanut butter, eggs, yoghurt, or smoothies so you're getting something meaningful in. Some mums find that what they can tolerate changes by the hour, so don't stress too much about "proper" meals right now - keeping calories and nutrition in any form is the main thing. Hope it gets easier soon, pregnancy appetite can be so unpredictable.
try small bites throughout the day or fruit smoothies throughout the day