Talk to General Physician on Cardiologist Anxiety Depression

My heartbeat has been fast for many days and when I suddenly get up or sit down, I feel the heartbeat and it is also fast, it stays fast even at night and if I get up at any time of the night, I feel my heart beating. And it is beatinh very slowly. Strange thoughts are coming to my mind. It seems like a heart attack will happen. Something will happen with me plz tel me what i should have to do i am very stresed with this is that any risk?