TTC...How should I handle this situation?

I am 23 years old, almost 24 and I am a caregiver for my elderly grandmother. Also, I am newly engaged. My fiancee who lives about 1 - 1 1/2 hours away has been frequently talking about having a baby. I don't work since I care for my grandmother but my fiancee makes more than enough income to care for a home, me and a new baby. My issue is I don't want to wait until I'm nearly 30 or older to have a child and re-start my life. I do have plans to start a career in the future but my grandmother is my main concern right now. Also, my grandmother is on hospice services. Therefore, a nurse can tend to her needs when requested. How can I handle this situation without my family members thinking I want to become pregnant to get away from caring for my grandmother?