Congrats on being almost done with your first degree
You have a lot of options right now considering your situation. Nurses in the Air Force have BSN's. From there, they can specialize into Obstetrics (if that's what you meant by midwife nursing?), ER, ICU, etc. Now to consider what path you want take to getting there. Are you more interested in a steady job with benefits right now? Or more interested in becoming an RN, BSN?
If you want to get into the AF right now, you would be enlisted personnel. They could put you in a role in the healthcare field, or they could not. All depends on the needs of the AF. The pay would be lower, but enough for a single person to pay their bills. After a year or two enlisted, you may get approval to take classes towards an RN program. However, the clinical portion of nursing school is extensive, and I don't know how they would handle that on top of your duties in the AF. Definitely something to speak to a recruiter about, or better yet, speak to current Airmen that might have similar goals.
If you are more interested in pursuing your goal of nursing, start looking at nursing programs
now. BSN programs are 3-4 years long depending how many of your current credits will transfer. The programs are competitive, so keep that GPA high. When you complete that degree, you'll be able to sit for the state board exam and come out of it as a Registered Nurse with a Bachelor's of Science in Nursing. These are the qualifications necessary to apply to the Air Force Nurse Corps. This is also a competitive process where they will look at your GPA, community service, credit history, work experience, criminal records (even traffic tickets), letters of recommendation, etc. If selected from the pool of applicants, you would be a commissioned officer in the Air Force fulfilling the role a registered nurse. Your pay would be competitive to civilian nurses. You may even qualify for student loan repayment and a sign on bonus (this past year was 30K for a 4 year commitment).
There's a ton on information on both processes in these forums. It wouldn't hurt to contact a recruiter to get more up to date information and answer any questions you may have. Good luck