I’m concerned...

So I’m not sure what it could be, but since the 6th I’ve been feeling nauseous all day and I have been spotting. I ended my period on the 31st and when it ends, it ends. But this time there’s been times where I wipe and it’s very little but bright red.. sometimes it stains my underwear. i am worried.. I do have the Nexplanon for birth control. I’m suppose to be renewing it in May. At first I thought I was pregnant but i took pregnancy test and negative.. I don’t want to go to the doctor and make a big deal out of it. Any suggestions?