If you have suffered a heart attack in the past, how likely is it that you will have another one.?

It depends whether you change your ways. I worked with a man who ate fast food every day and never exercised. He has a heart attack at 40. He changed nothing about his life. I doubt if he is still alive. 

People need to eat healthy food and get regular exercise. Being overweight and under stress can kill you. If a person who has a heart attack cuts down on red meat, walks every day and maintains a healthy weight, he or she can live a lot longer. 

After surviving a heart attack, you're probably certain of this: You don't want another one. Yet, about one in five people who have had a heart attack will be readmitted to the hospital for a second one within five years. Each year, there are about 335,000 recurrent heart attacks in the United States.

Very likely, me Dad had five in two months.

--  It is quite common for a person to have several heart attacks.

--  My mother had 3 heart attacks over two years and died from the third back in July 1972.

I had a heart attack at 21, and haven't had another since. I have a lot of panic attacks though.

Very likely, me Dad had five in two months.

About 99% likely.

depends on what you do to try and prevent another one

That stat is available online and recurrence depends almost entirely on dietary changes.