The most common reason that people even NEED terms for themselves is to introduce their partner to another person. The two people already know how they feel about each other. That doesn't change just because you assign each other a title!

So the next time you're out in company, simply introduce your guy or girl as "My Darling, Chris" or "My Darling, Pat". That shows pretty clearly that you two care for each other without having to narrow it down to a specific "level of commitment".