Help me figure this out!

This month Between 5/24-5/27 I had brown discharge(tmi) it was only when I wiped and a little in my underwear over night so I went to the doc on 5/27and they did a pregnancy test that came back negative then this week I've had this pressure below my belly that's not like period cramps. I have taken a couple home test that I got from the dollar tree but all BFN so I'm going crazy trying to figure out what's going on. I also have sore nipples to the touch I usually get sore boobs befor my period but still no AF I'm irregular I have like a 48 day cycle so idk what's going on. Please give me some advise