Pregnant/something else? And back pain.

My home urine pregnancy tests were negative several times and doctor's lab test was faintly positive but vaginal scan did not show anything, i should be 6 weeks pregnant.Last month(February) i got my period a week early ie on 3rd February. I usually have a 3 day cycle. I was on the 3rd day of my menses, blood flow had stopped. On that day My husband rubbed his penis on my vagina and clitoris. No sexual activity later. This month i got just a one day bleeding with cramps on 3rd March. Now i feel breast tenderness esp on the left side, frequent urination, nausea, mood swings, fatigue, giddiness, bloating and constipation, cramps and heaviness in the lower abdomen while turning sides in bed, pain and heaviness in pelvis and pubis, weakness and hip pain and back pain.