headpain back of my head and feel dizziness

Hi,
A very warm welcome to the forum.

Basically your symptoms are generalised and not pointing towards one particular disorder. The headpain at the back of the head can be due to muscle spasm of the occipitalis and other muscles of the scalp.

The spasm can be so intense that the muscle will feel bruised or sore even after the tension has been released.These muscle spasms then cause primary headache like tension headache.Apply alternate warm and cold compresses,elevate the head while sleeping and take some over the counter NSAID analgesic(pain reliever) like ibuprofen(advil/motrin) or acetaminophen.

Jaw cracking can be due to jaw dysfunction which can be due to grinding or clenching your teeth (bruxism), especially at night, biting your nails, holding things between your teeth, stress or injury. Chest pain can be due to gastritis for which you should take small frequent meals instead of a heavy meal. You are quite young and at such a young age, chest pain is usually non cardiac in origin. However it is not normal to have dizziness and for its evaluation, you should consult a physician.

It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care.