Last period june 22-26 it's august 11th sexually active july 18th. lower stomach pain, running to the bathroom, and gas. what's happening?

Missed period?: Pregnancy is the most common cause of a missed period. If not pregnant, other causes of a late or missed period include: excessive weight loss or weight gain, increased exercising, emotional stress, having an illness, traveling, medicines (especially birth control pills), hormonal disorders, etc… One can do a home urine pregnancy test 3 weeks after sex, if worried about pregnancy.