Matthew is correct.  No sin is involved.  If you fear the doc is checking you out, request a witness of your gender to be in the exam room.  He needn't look, just sit in a corner.  If something is wrong, you can yell.  Not taking an exam from time to time when it is available to you is neglect of your health.  That IS a sin, especially if you have dependents who will be harmed by your incapacity or untimely demise.  Take a lesson from a friend of mine, who, in 1995 decided to 'rely on the Lord' to take care of her serious chronic illness.  She ruptured an artery and bled out and died on the floor of her apartment. Her body lay there until her fiance forced his way in and found her.  She'd been dead three days in 95 degree heat.  In another instance, a relative refused to consult a doctor about his terrible cough.  He died of lung cancer that could have been treated.  He left his wife, mother, and seven children.  If you prefer, go to a "naturopath" instead of an MD.  Be thankful you have medical care available to you.  Many have no choice but to wait until they become seriously ill before a doctor will see them.  
Don't worry about your female doctor.  Like all physicians, she sees unclothed folks all day long.  You're just one more.