You can exclude or confirm a pregnancy in a very simple way: by taking a home pregnancy test. The symptoms you mention (cramping, nausea, headache, dizziness…) are common in many conditions and they are not evidence enough to diagnose any particular disease. You can visit your GP (general practitioner or family doctor) for further examinations to identify the cause(s) of your symptoms such as a physical examination, standard blood analyzes with sedimentation, and an abdominal ultrasound.