Hi, Can U Tell Me How Often A Mammogram Is

Hi, can u tell me how often a mammogram is recommended I am 50. yesterday. no history any family for breast cancers. I take estrodial since 05. and for about 3 yrs thyroid. but i think its time for that to start going i have chgd my life style to healthy organics and exercise lost 75 pounds or so in 14 months i run apx 4-7 miles a day 5-7 days a week. I have had 2 in the last 3 yrs. I find that a bit much for a time to reschedule card. and wonder if the X-ray gives me more of a risk. I also have had extinsive dental work this yr with many X-rays. So my question. how often do u recommend?