Has anybody heard of cryptic pregnancy

Alexandria • 22 years old ftm
This is suppose to be my first pregnancy but I'm not showing at 18 weeks barley feel any movement how ever my symptoms come and go like nausea and hunger some days I don't even feel pregnant at all. Today I got these dull stabbing pains in my lower stomach and I wonder if its one of those (i didn't know I was pregnant)* situations*