Implantation Bleeding: This is a common cause of spotting in early pregnancy, occurring when the fertilized egg implants into the uterine lining. The timing (5 weeks gestation), symptoms (small amount of blood, slight cramping), and the fact that the patient has not had a check-up yet, make this a plausible diagnosis. The patient's report of constipation and harder than usual bowel movement could also contribute to the cramping.

Threatened Abortion: Any bleeding in early pregnancy could be a sign of a threatened abortion, where the pregnancy is at risk but still viable. The presence of cramping and spotting, even if minimal, warrants consideration of this diagnosis.
Urinary Tract Infection (UTI): Given the patient's symptoms of slight cramping and the fact that the blood is noticed when wiping after urinating, a UTI could be a possible cause. However, the absence of other typical UTI symptoms like dysuria or frequent urination makes this less likely.
Constipation-related Hemorrhoids: The patient's report of constipation and harder than usual bowel movements could lead to hemorrhoids, which might cause spotting, especially noticed after wiping.

Ectopic Pregnancy: Although less likely given the early gestational age and the nature of the symptoms, ectopic pregnancy is a life-threatening condition that must be considered in any pregnant woman with abdominal pain and vaginal bleeding. The risk factors for ectopic pregnancy (e.g., previous pelvic surgery, history of ectopic pregnancy, or infertility treatment) are not mentioned, but it's crucial to rule this out.
Molar Pregnancy: This rare condition can cause early pregnancy bleeding. While it's less common, the presence of any abnormal uterine bleeding in early pregnancy should prompt consideration of a molar pregnancy, especially if accompanied by other symptoms like excessive uterine size or severe nausea and vomiting.

Cervical Polyps or Cervicitis: These conditions can cause vaginal bleeding, including spotting after urination. However, they are less likely to be directly related to the early pregnancy symptoms described.
Placenta Previa: This condition, where the placenta covers the cervical os, typically presents later in pregnancy with painless vaginal bleeding. It's rare for it to cause symptoms as early as 5 weeks gestation but could be considered if other diagnoses are ruled out and symptoms persist or worsen.