How can I be sure I don't have schizophrenia? Could I be just starting down the road to it?

It's obvious. If you are 30 or older, forget it as symptoms show up sooner. For some people it's as young as early childhood and the symptoms are very evident as with hallucinations or delusions. Often there is some family history of the illness.
What worries you? It's hard to answer your question, because you are focused on a diagnosis and don't describe what is happening to make you concerned. If you believe your mind is "playing tricks" on you or others are noticing behaviors they find odd, then you might want to see professoinal, probably a psychiatrist to explore your behaviors and see if there is a problem.