What Causes Lower Back Pain,bloating,breast Pain And Brown Vaginal Discharge?

Hi my names Leah. The first day of my last period was the8th of may I had withdrawal sex with my partner on the 20th of may since then I've had lower back pain queasy tummy period like pains and bloating my boobs ache off and on my period was due yesterday 5th of June but didn't come then today 6th of June I started having brown discharge but not enough to fill a pad was very light. Could I be pregnant and when will the best time be to do a HPT please help!