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From very less information like that it is difficult to come to a conclusion.But lets try with a few conditions .If you have missed your period , you could be pregnant and having high volume of blood which is normal sometimes and needs evaluation sometimes.
If not , you could be having hypertension
and so you feel pulsations.There are chances that you could be having a heart problem also.If this is a muscular problem unlike the above feature , please get evaluated by an Orthopedician.
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