crazy period, HELP COMMENT THOUGHTS!

okay so i had unprotected sex from june-august . in june my cycle was 2 weeks late so of course i had a pregnancy scare, the test was negative though then in july it was a couple days early but then in september i was spotty for one day i wiped and it was light red but it was only that one wipe . but my thing is , my cycle has been starting off brown and light & remain light throughout the whole 3-4 days. can someone explain to me why does it be like that , why does it start of brown when brown represents old blood but ik it cant be old blood when its the start of a fresh period , help !