Need some advice!

Monica • 26, married, step-mommy to two lovely little boys. TTC since 6/2017.

Here’s the run down! My last period started 12/5/17... it’s known for being sporadic. I took the first test on 1/2/17 and the second on 1/3/17. Today I had an ultrasound due to my past ovarian cysts. The tech said she still couldn’t see anything that would indicate pregnancy. This would be my first pregnancy so I’m lost! Is it possible to get a positive at home pregnancy test and it still not be visible with on the ultrasound?