Nausea

I have noticed I have been having bouts of nausea for about 4 days now, around the same time everyday, between 4-6pm except last night it was all evening, I take my prenatals in the morning with breakfast, and feel fine all day until I reach home after work. I don’t know if it is the prenatals causing this, since I have been getting BFN-my AF hasn’t shown up since last Thursday. Will test again in a few days. But wondering if anyone has experienced nausea in the evening? I have never felt nausea before or after AF until I started taking the prenatals. I am on CD 31.