Pregnancy

So I’ve been having bright/light pink/light brown spotting that never shows up on my underwear but it shows up when I wipe. I’m now 18 days late on my period and I had a blood test done and my doctor told me it came back negative but still no period and just experiencing the spotting for about 2 weeks now. I’m super bloated and I have a faint dark line going up to my belly button. My doctor told me that’s what people get when your stomach expands (which I think is a lie, normal you get stretch marks). I don’t know if I should get a second opinion because normally i have heavy periods and blood clots and I haven’t had any of that... what do you guys think?