Sick with worry. Help

Need some words off advise from some off you who have been pregnant before. I got my BFP on Monday making me just over the 4 week mark. I can't shake this feeling I have that am maybe not even preg at all or it won't reach out to even 6 weeks. Anyone else like this? It's sort of bringing me down and I know some people would kill to be in my shoes. I just don't feel pregnant it's really hard 2 explain.