Congratulation, what a fabulous news.
I was worrying about the same: lines were not dark enough, but my doctor said I should not trust the test to judge HCG level, so do not worry and make a blood test. And quit testing. I really stopped temping and testing because if I see that faint line it will make me crazy. SO I am just waiting till my 8 weeks ultra sound. Getting nervous is the worst you can do because when you feel scared your uterus is contracting. That is the worth you can do to your baby. I know it is hard not to, but trust me, I have anxiety all the time. But this time I said to myself Nothing I can do and I am not in charge, if something bad happens, there is nothing I can do. So I decided to trust Highest Power and absolutely surrender to any outcome.
Meanwhile I just wait and try to stay positive. Do not let your fair scare you. Relax and think about your future baby.
Hugs.