I am sorry to hear about your medical problems. Lump in the clavicle region could be a lipoma (localized collection of fat), a swollen lymph node, a metastasis of a cancer else where, a tubercular node, a neurofibroma (collection of nerve and fibrous tissue) or a bone or muscle mass. This has to be diagnosed by a CT scan or an ultrasound.
Headache with dizziness can be due to compression of the spinal nerves in the cervical spine region. This can happen due to overuse of computers, work involving straining of neck, herniated disc, canal stenosis, bone disease, spondylosis, poor posture etc. A MRI of the cervical spine and nerve conduction studies may be required. Please consult a neurologist. Get your blood pressure checked. This can also cause headache with dizziness.
TMJ is another possibility. If you have been out in sun a lot or drink less of fluids then it can also be due to electrolyte imbalance or dehydration. Benign intracranial hypertension also causes dizziness with headache and a spinal tap is confirmatory. It can be a migraine attack too. Other conditions to be strongly ruled out in your case could be Meniere’s disease of the ear, wax in the ear, infection of the middle or inner ear, and benign positional vertigo. Hence it is important to consult an ENT specialist and a neurologist too.
Other causes are anemia, hypoglycemia or low sugar and some endocrine problems, such as an underactive thyroid (called hypothyroidism), overactive thyroid (called hyperthyroidism), adrenal insufficiency (called Addison's disease), and in some cases, diabetes, may lead to hypotension and hence lightheadedness and an off balance feeling. It can also be an anxiety and panic attack. It is really difficult to comment on the net.
In your case anemia and low vitamin D can be contributing factors. Please consult a doctor. Take care!
The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you. The advice may not be completely correct for you as the doctor cannot examine you and does not know your complete medical history. Hence this reply to your post should only be considered as a guiding line and you must consult your doctor at the earliest for your medical problem.