Please don't just view I genuinely would like to hear your thoughts please, and no rude remarks!

Ok so my period is due this Saturday, last week I spotted light amounts of brown discharge for about 4 days, now it's back to a clear/milky white, my breasts have been hurting but more tingly nipples than unbareable pain? Feeling extremely exhausted, headaches and slight cramping and very slight nausea at different times of the day etc, I tested yesterday but got a negative so I'm just wondering could this of been implantation and I've just tested too early? Or am I overthinking things? But surely if you have symptoms you'd get a positive?! Also a bit of info as we aren't actively ttc, basically we've have unprotected sex but then taken my birth control pill that evening (but not on it daily/regular) please advise?!