Morning sickness?

Im confused! Just had my BFP over the weekend but have felt "off" since last week. I believe I'm about 4 weeks today. I don't know if this is what morning sickness feels like? I notice as soon as I start to feel hungry if I don't eat something right away I start feeling really nauseated. I'll eat, then feel sick for a bit. After a while though, I'm fine. In the middle of the night last night I woke up really hungry and was almost sick. I wasn't hungry when I went to bed! Is this in my head or is it morning sickness?