Help pls!!

I'm 15 days late on my period but took a One Step pregnancy test on the 14th which came back negative, but apparently I didn't take it right according to someone I know. I took it but didn't even set it down 10 minutes because I thought it was automatically negative but when I check an hour later it had a faint line.
I've had tender nipples but my boobs feel heavier and fuller. I've broken out in rashes and my boobs and stomach feel itchier than usual, I've even seen new stretch marks. I've been having cramps, gassy, nauseous, dizzy spells and fatigue. Should I retest? Also, what were your pregnancy symptoms and how early were they?
Right after I took it
An hour after I took it