Richard,

Let's look at the situation objectively.

You're Catholic but not married in the church. That means that you are not married in the eyes of God. Since the woman you are with has no annulment but was previously married, that means you are, objectively speaking, committing adultery every time you make love to her. Even from a legal perspective you're committing adultery, since you imply she was never divorced. (You said she never separated.) By the very fact you are asking the question, you show some awareness that what you are doing is wrong. You are in a very grave situation.

• Ask yourself, what are my intentions in asking this question?
  

If your intention is to justify continuing in your situation, to justify committing adultery, in hopes that you can continue as you are but at the last minute you can repent and get a clean slate, that is the grave sin of presumption: Trying to take advantage of God's Mercy. To be forgiven of your sins requires a sincere commitment to turning your back on the sin, not committing it again. You can't repent in advance while intending to sin in the meantime, since repentance requires a sincere commitment to no longer committing the sin.

Suppose she decided to cheat on you, but resolved, if it ever came to a head and you found out, that she would just say she was sorry and make up, but intended to cheat in the meantime.

• Would her apology, when you found out, be sincere and worth forgiveness?

I'm betting you would say no, it isn't; it's insincere. The same is true if you plan to repent at the last moment while also planning to continue sinning in the meantime.

Even if such a trick worked, you are assuming that you would have that one-second chance to accept Christ. (Suppose you die instantly in a car crash?) . . . and that you would be able to marshal sincere repentance after a lifetime of sin.

It's like expecting to instantly jump up and dance after being immobile in bed for years. It's a very big risk. You're risking your eternal soul. So not only is this theologically bad, it's bad from a practical standpoint.

"I tell you, now is the time of God's favor, now is the day of salvation."

(2 Corinthians 6:2)

Have your partner get a divorce and an annulment, then get married in the Church and receive the Sacrament of Reconciliation now for all the years you've been living this way. Then you will be on the road to salvation.

I know it's tough, but if you're a man, you'll do it, because it's the right thing to do.

Eric