It's called aromantic or "single at heart" when someone tends to feel like that their whole lives.

Not sure how common it is for someone to switch. Several years ago, I went through a brief phase of wanting a romantic relationship. (I didn't want one when I was a kid, and I don't want one now, but for a year or two in my early twenties, it somehow appealed to me.)

Even for people who do want romantic relationships, it's not good to feel "dependent on relationships to feel complete."

Looking at purely a practical standpoint rather than emotional, it seems like a relationship would be disadvantageous in your circumstance.