Return of morning sickness?

So I'm just about 19 weeks (almost half way!!!) And I have gone past morning sickness, but now it's like it's returnes. It only happens if I don't eat. I tried healthier snacks, but I need something substantial and filling. I have gained nine pounds which is normal and good. But I'm worried that with this new form of morning sickness I'll gain more. I have a really active job so by the time I get home I'm exhausted. I can't even imagine working out more. Any advice?