9w3d - so nervous

anyone else really nervous about miscarrying? it basically consumes my whole day ... I have been crampy and had one streak of blood in cm on Monday ... my nipples aren't as sore and I'm not as nauseous ... I've read that it's normal for pregnancy symptoms to come and go but I can't stop feeling like something bad has/is going to happen! my 7 week ultrasound showed a strong heartbeat of 145 and my dr. said everything looks perfect, I just can't stop worrying!