Hey there. I'm 20 wks and this is alos my first pregnancy. Light spotting can happen a lot during pregnancy , and I believe its more common early on.
I know exactly what you mean by the nervous thing, I spotted a few times during my first trimester and spazzed every time. You should be fine , unless like you said you can fill a pad or have any pain or cramps. Then it's time to get to emerg. Or to your doctor.
Try to relax, the calmer you are , the clamer baby is and thats what will make you feel most at ease.
Good luck with everything !