You seem to have erythematous patch on chest ,upper part, I think V area..
There is burning sensation also.
It is exacerbated by sun exposure.
So, with this much history, I feel that you may be having photosensitive dermatosis or photo allergic dermatitis
I firmly advise to consult dermatologist
Blood tests may be done to rule out connective tissue
diseases..like lupus erythematosus
.. and other systemic diseases.
Avoidance of sunexposure would be the main thing to follow.
Cover mechanically by clothes or sunscreen to prevent further spread.
After firm diagnosis, expert might treat the disease.
I hope you got my answer.
Dr. Ilyas Patel MD