I wouldn’t worry until you get your results. My pregnancy test looked exactly like that the day *before* my period was due and it was a singleton pregnancy. Btw twins runs in my family (my mom’s a twin). So like I said, I wouldn’t worry!
I had symptoms very early on and had a dark pregnancy test at 3 weeks and I’m totally freaking out about multiples too. I don’t have my first appointment till 3/7 so I just have no idea 😩