That is low, but it would be best to ask your doctor about this. I'm sorry they haven't said anything about it to you, but have you asked him/her? There are some people that are really fit that can have that low of a heart rate and 55 - 60 is the lowest that I've seen, but depending on fitness level, someone can have lower. With your blood pressure being low too, it would honestly be best for you to call and talk with your doctor as they have all of your health history and can tell you whether you should be concerned or not. If they say it is a concern, ask them flat out about what you can do/should be doing. They may not have realized that they didn't mention those things to you.