Please answer...What should I do?

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. My fiancee and I don't plan on getting married for another year or so. However, he did bring up the idea of my grandmother moving in with us because a nursing home is not an option. Also, I'm not rushing or hoping for my grandmother to pass away but I don't want to get married and 3 years or so into the marriage we still don't have a baby. This situation is making me feel as if I need to choose who and what is more important to me. How can I handle this situation without my family members thinking I want to get pregnant to get away from caring for my grandmother?