At home pregnancy test

I took 2 family planning early results pregnancy test.. The first one I took about 3 weeks ago was a light line in the result window. I took the second one today and it has both lines but I up it up right side up in the box and the line is pretty light but most defiantly dark enough to see. So my question is how often are the at home pregnancy test wrong... My husband and I really want a baby so I don't want to get my hopes up and can't get into a doctor for a few weeks but if I'm pregnant I don't want to stress out over it and lose the baby