Brief Answer:
Possible dehydration and orthostatic hypotention.

Detailed Answer:
Hello,

Thank you for using Healthcaremagic to post your health query.
I read carefully your question and I understand your concern.

Your blood pressure, especially the diastolic is very low. That is why you are feeling lightheaded and all the other symptoms.
I would recommend resting, keep your feet elevated above your heart level and drink plenty of water. The problem can be from dehydration, because it is hot and it happens in summer.

If worse or not better after doing what recommended after one hour, I would recommend going to the ER so they can run some tests and see directly what is going on with you.

Hope this is helpful.
Let me know if you have other questions or concerns regarding this issue.

Regards,     
Dr. Papaqako

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