Your symptoms of stress, tightness of muscles in the neck, shoulder area, and headaches suggest of tension headaches. The causes of Scalp
tenderness are Migraine
, Tension headaches, Cellulitis, Cervical myelopathy, Contact dermatitis, Malignancy, Scalp injury , Squamous cell carcinoma, Brain tumour and basal cell carcinoma. So scalp tenderness may also be associated with the tension headaches. Please go for an MRI of brain and spine to rule out other possibilities.