my period cycle is usually 35-42 days. i have had a lighter period than normal with no pain. about a week or so before this i had cramping and no period. excessive gas, feeling sick at times on and off, light headed at times. lower back pain for about 4 days nows. pain alternating from left to right periodically. light headaches for about 4/5 days. negative pregnancy test????? could i still be pregnant, when should i test again?