The condition one may have when they have been retaining their fecal material (intentionally or not) longer than the body would prefer, causing upset stomach, headache, and nausea, not unlike that of morning sickness with a human baby, except the symptoms will immediately go away with a good poo session. Now you're just pregnant with a poo baby.
Tyler: Oh, God! My stomach! I feel sick!
Kyle: Do you need to shit? Have you gone this morning?
Tyer: No I haven't. What's that got to do with anything?
Kyle: Man, you got morning shit-sickness! Go take your morning dump and you'll be good to go!