Why did I vomit immediately after eating?

Last week while doing my cousin's hair I vomited out the blue. Now I recently have been feeling a bit sick and had a slight headache with a bit of stomach nausea. So I decided to get something to eat (a hot pocket and a glass of lemonade) immediately after eating I felt really queasy and suddenly vomited in the toilet. My husband and I have been trying to start a family, but I'm a little skeptical because I've had symptoms before but was negative. Another thing my husband keeps pointing out is that my stomach has gotten a bit swollen and my period lasted only four days this time instead of the usual eight. Another symptom my husband brought up was my sleep habit, which I have to admit has been more than usual. So, please give me some insight on what you think. My husband and I really want to be pregnant and will get an HPT tomorrow.