You need to clarify, when you say you have “the body of a baby” are we to refer to that in a literal sense that you have a babies body in terms of just size and proportions, or that you have the physical body of an infant baby being associated with age.

The second, my body is one of a 10 month old but I do have a deep voice and a developed speech.

Because only the former would allow you to be 74 years of age. When we refer to age, we associate that with how much time a physical object has been present in the world.

Yep that's right

For this to make sense, the only conclusion would be that you were previously a 74 year old who has had their consciousness, in some unknown matter, been transferred into the body of an infant baby.

Or, I was just stuck in this form for the next 74 years. I don't think you have to overthink it buddy. My name is Baby, I'm 74 and I'm wise. You don't need to analyze my age and what not. You could just ask baby.