Irrational fear of chemical or miscarriage

We had a BFP yesterday and we are so excited! Had blood work done, waiting for results. But, I can't shake the feeling like something isn't right. I'm not having any cramping or spotting but I'm just fearful because the 2nd lines are not very dark. I keep waiting on them to get darker but they're staying about the same. Also, I took a digital and got a negative (not with FMU). I know it's still early (about 3-4 weeks) but I'm starting to worry myself. Any words of advice or encouragement?