I havent had my period in 4 months. is that normal? im also having pain in my vagina and lower stomach

Usually not normal: A urine pregnancy test, done correctly, gives a reliable result 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and thus lead to a repeat test. If a woman gets her normal regular period, then she is not pregnant, and a test is not needed.

May need lab tests: A urine pregnancy test is definitely the best thing to do first. If it is negative and period does not come, a Dr evaluation for other causes (thyroid or pituitary problems or a few others) can be done. Stress could possibly do this but other causes should be ruled out 1st.