nauseous again?!

I had a lot of nausea from 5-11 weeks. Now at 26 weeks it's occasionally back! 
Not as bad, but still I'm curious if anyone else has/had this. 
I sometimes feel like I feel weak like nauseous from needing to eat, but I just ate!
I also wonder if it's my prenatal vitamin. I couldn't tolerate it in the beginning so I switched to gummies but just re-started the regular pill.