nauseous all the time

Hi, so here's a little background I wake up every morning and I'm super nauseous!! Brushing my teeth is a struggle and the thought of food makes me want to gag, I thought I could be pregnant at first but I took tests and they all came back negative.... So what could it be I'm not on any birth control ( doesn't work with my body ) and I eat pretty regularly and healthy. Let me know thank you 🌻