1) It is important that you understand the main limitation of the proposed methodology - it only measures the proportion of women using contraception. It does not consider whether the respondent is currently pregnant, trying to conceive a baby, whether she has a sexual partner, and other reasons for not using contraception. If you want to assess the proportion of women who currently do not wish to become pregnant but who are not using a contraceptive method (i.e. the "unmet need for family planning"), you will have to use a much more complex methodology (read guidance at Measure Evaluation's website).
2) Consider including additional question assessing the main reasons for not using contraception. If the answer to Q1 is "no", you can ask:
Q: What is the main reason why you do not use a contraceptive method?
A: (multiple answers possible)
1) does not have a partner
2) does not have sex
3) is currently pregnant
4) thinks that she is pregnant
5) wants to get pregnant
6) does not agree with using contraception (for religious or other reason)
7) her partner does not agree with using contraception
8) someone else in her family / community disagree with her using contraception
9) does not know any contraceptive method
10) does not know where to purchase contraception
11) feel too shy or affraid to go and purchase contraception
12) the contraceptive method she uses is not available
13) does not have money for purchasing contraception
14) is affraid of contraception's side effects
15) is exclusively breastfeeding
16) other reason - specify: ...........................
3) This topic can, in many contexts, be very sensitive – consider therefore only having women as your interviewers.