Hi! I had gone through your question and I understand your concern First I would say that the first (top)number in a blood pressure reading is the systolic blood pressure and the second number is the diastolic pressure .So you mean 90 the systolic and 50-60;the diastolic . We say normally that the patient has low blood pressure when it s lower than 90 -60 one of them or both ( systolic or dyastolic). I would ask you some question : -is the blood pressure only low after you stand up ( for that I would advise to measure your blood pressure first when you lay down and after that after you stand up , if the blood tension drops after you stand up .If you have a drop with 20 mmhg in your systolic pressure or 10 mmhg in your diastolic blood pressure .probably you have orthostatic hypotension -does it only drop after you stay for a long time stand up - does it happens only after you eat .( measure it after eating . If you find the answer of these question when you go to your treating doctor will help for a fast diagnosis. lipidor can cause muscle pain and being tired . I would advise you to manage stres , drink a lot of water ( of you had diarrhea, fever , vomiting can cause low blood pressure) , eat sweet Food ( low blood sugar can cause hypotension) . If you have any chest pain call the hospital . Call your treating doctor to find out the real reason of your low blood pressure ,He will do some examination to exclude any heart problem (ECG ) , blood test ( muscles , sugar ) . Wish you good health . If you have any additional questions please he free to ask me .