Constant near fainting. Need to consult?

Hi, 5 days back, I felt like fainting but didn't faint. I was walking for few mins, drank water and left home. After that, I constantly feel like near fainting whenever while standing or sitting, I don't have fainting sensation while lying down. Feeling very tired, feel like I'm not balanced and may fall down. If I walk for few mins, I feel very tired and sleep for some time, after that it will be little ok. My both ears are blocked but able to hear. Sometimes my heart beats fast. Last month I did (ECHO, TMT, ECG) everything is OK. Yesterday, I consulted a neurologist, my BP was 100/70 (i think this is not LOW BP) and he told me that I very stressed and have anxiety. He prescribed me few tablets including some tablet for SOS Anxiety (i need to take whenever my heart beats fast). I'm really worried about my health. What could be the issue? Why I daily feel like near fainting sensation, body tiredness, dizziness? Which specialist do I need to consult?