Hi abdelghany,
I would recommend that you see your doctor so that he/she can determine the reason for your heart rate remaining elevated. There are many reasons why our heart rate might be elevated. In your case, it may relate to anemia or as you say may be the body adjusting to having steroids withdrawn.
An ECG will confirm your heart rate. Blood tests will help in exploring your electrolyte balance (sodium, potassium, calcium, magnesium). If a persistent increase in heart rate is confirmed, an echocardiogram might be considered to ensure the heart structure and function is normal. Occasionally we need to use a heart rate monitor over 24-48 hours to properly measure the heart rate and whether it changes throughout the course of a day.
I can understand you being scared but don't let yourself be paralyzed by this fear - simply discussing your heart rate with your doctor and working out a plan to assess it (and treat if necessary) will help to reduce your stress.