We bump into things constantly without noticing. You could have iron deficiency anemia, vitamin K deficient.Health supplements like garlic, and fish oils could be the cause. Older people bruise easier due to broken capillaries and thinner skin. See the doctor is it continues. ( I saw you have 3 kids, that alone is reason to be banged up : )
What you are observing on your thighs might be a case of subcutaneous hemorrhage. Subcutaneous hemorrhage is when the minute blood capillaries or vessels just under the surface of the skin break and leak blood. Talk to your doctor for medical advice and proper diagnosis.