Answer 1) Being an Medical Assistant, makes you authorized to ask about patient's information related to their medical history. One can start by asking physical history or any complications in their reproductive health and once the patient becomes comfortable and open enough to share everything, questions related to usage of birth control can be asked.
Answer 2) Patient's age is an important factor in discussing or answering questions on birth control as young mother's would feel shy to share their sexual well being compared to the mother of late 30's or 40's who already have more than 1 child. An experienced women who has undergone pregnancy more than once will be able to express more and understand the problems, she will talk openly and freely; whereas a new young mother will be hesitant to discuss about the reproductive health and also about the birth control measures.
Answer 3) An individual's economic status has great impact on the usage of contraceptives, as the birth control measures are available starting from cheap contraceptive pills to expensive hormonal therapy. The economic status of the individual will be the deciding factor for the choice of contraceptive that individual may use.