Queasiness & IF?

I’ve noticed lately on an IF day I’ll experience a bout of queasiness (like a sourness in my stomach, esp after drinking water) – no stomach rumbling or anything with it but it’s definitely not a pleasant physical feeling. I’m experiencing this now and wondering if it’s normal and what it could be? I’m slightly hungry (it’s been about 18 hours since my last meal) but def not starving – just wondering what to make of this signal ? Thanks!