Linea nigra

So I noticed today that I got this line in my stomach as far as I know this line comes out when your pregnant and for some girls just have it since they where small but is it normal for it to just showed up all of a sudden? I don't think am pregnant but am also not 100% sure am not just because in may I missed my period so I took a hpt when I was 3 days late and got a faint positive but since I saw the test at 1 min mark and look negative I came back 15 mins and their was a faint positive with color and everything I didn't think much and didn't bother to retest......turned out about 3 weeks later I got my period but it was a weird period (TMI) blood was dark and had cramping on and off all week, and blood wasn't coming out as much as it usually would like if it was all clogged up their with all the cramping I expected a very heavy period not a medium to normal period (I never cramp all week maybe just on the first day but that it) also let me say my period was really regular same day each month regular. When I first missed my period I had lots of nausea dizziness then it all went away recently my stomach has been bloated (been bloated since I missed my period in may I usually get bloated before my period but after my stomach flattens a little and this time that my period end I just stayed bloated, extremely tired always sleepy and lots of flutters and twitches in lowers stomach, hip discomfort, extreme thirst ,frequent urination (I never used to get up at night to pee now I get up like 2-3 times at night) cravings and I feel like am coming down with a cold for the past 2 weeks so what do y'all think is this line a sign that I should retest?