I've gotten that way a few times too mommy. I stay to myself a little while, say a little prayer, think positive about my baby or look at his little clothes we brought, regroup, then socialize again lol. I can get grouchy for no reason and don't want to make my family feel bad.
Just try to think more positively and don't focus so much on yourself but rather the health of your baby. Being too depressed can cause harm to your baby