What Causes Spotting With Dizziness Despite Normal Periods?

hi i was due on my period on the 13th may, i had unprotected sex on the 11th may, my period came on the 27th may but i normally have 7 days of pain and heavy bleeding, i had 4 days of bleeding but not heavy and no cramp, that lasted till the 30th may then on the 10th june i have had spotting startted off really dark brown then went a pinky brown and stopped yesterday the 12th, i havent felt well at all i have had low backache, headaches, feeling dizzy and exhausted, my periods are normal every month and have never had this before, im just unsure whats going on