Nausea during second trimester...???

coromble

Ok, so I had literally NO morning sickness during first trimester.  Did not throw up even once!  Now, I'm almost 19 weeks and three times in the past few weeks I have like dry heaved or thrown up like a little bit of liquid from my stomach.  Sorry if that is TMI, but I need to know, is this normal?

Twice it happened when I had taken a Tums or Tylenol on an empty stomach, but this morning it happened when I woke up and hadn't had anything to eat or drink.  I'm wondering if it happens when I'm hungry, but I've eaten breakfast since then and I'm still feeling a little weird. 

I might be freaking out because I'm a teacher and at school and I'm worried I will throw up in the middle of class!  Also - I just want to make sure everything is okay with Baby.

 Anyone else experiencing this?  Any advice?  Should I call my dr?