Should I be concerned about a small amount of blood in my stool (7 weeks pregnant)?

Yes. Blood on the surface of the stool or on your toilet paper is most likely from hemorrhoids and not uncommon or worrisome. If the blood is in your stool, it is more likely to be from higher up in your digestive tract. Causes range from infection, polyps of the colon, colitis to ulcers. None of these are normal for pregnancy and would require investigation.