Welcome to Healthcare magic. 1. Pregnancy can occur with 25 days cycle. 2.Pregnancy test is of value after missed period most of the time. 3.The symptoms does feel like gastroenteritis, and seen in the pregnancy as well. 4.Do one thing. repeat test after one week. If symptoms persists and test positive get an pelvic ultrasound scan done. Any question ? don t hesitate. Thank you.