For once I am NOT or at least trying not too
First off, your problem is psychological. If I didn't assume you were a dude I would've immediately labeled you as a girl. (Between the ages of 16-24)
The reason for this is simple, it takes more or less 6-8 months for the "honeymoon period" to be over. The lust then goes away and *should* turn into love (6-8 months is pushing the boundaries)
So then you decide to move on. This indicates you're thinking with your genitals. Before jumping in cock first (excuse the language), why not get your brain (the part in your skull) to help you think things through emotionally before you stick it in so to speak. You are going through a divorce... with who? a 3rd woman?
You also obviously do not think before you speak. You let your 2nd brain take over. When you went to Lady Gaga to tell her you can't see each other anymore because you don't feel the same way, your "pity" emotion flared up triggering you "OMG what if I can't bone her anymore" emotion because you're unsure (for the first time in a while it seems) if the other lady that you "love" will be with you or not. So then you turn it into a commitment instead of breaking up and being honest.
You obviously do not do so well in a face-to-face situation because of brain #2 and your inability to think logically while emotions (and fear) runs wild.
I'd recommend writing a letter. Not an e-mail. Give that letter to her in a face-to-face situation and ONLY speak after she's read the whole thing. You then have the opportunity to do the whole face-to-face thing and get it over and done with without little mr.bex coming up with his schemes of being able to bone 2 girls at once "just in case" **** doesn't work out.
I hope you're more mature than the 21-25 category I'm placing you in.
Also, I would say that you do not love Lady L. You lust after her. Lust is a pretty strong emotion capable of screwing with your mind making you believe you're in love with her. I could go into the psychological aspects of why this is but I'm not sure you'd understand entirely. It is very difficult with someone "in love" to take advice from someone else.
As an example, one of my friends said I should dump my ex because I wouldn't be able to come back from a situation like that. He was right. I was wrong. Stuff gets confusing on how people react.
Drop both of these women.
Try being single (and by single I mean DO NOT STICK YOUR PENIS IN SOMEONE ELSE!) for 2 years at least. Try to separate your emotional need for satisfaction and having the "in love" feeling with the real love feeling.
I go through an exercise where I say to myself "I just got castrated accidentally, she got old, would I still want to be with her?"
I can tell within the first 2-5 minutes if the girl I want to bone would be the girl I won't mind boning when we're both old and wrinkly. Love <> Lust. Learn it. Love it. Live it.
And like I said. Think before you speak, because you obviously don't, so refer to my letter writing method (NOT EMAIL)
*edit*
And I'm pretty sure you'll grow tired of Lady L and do the same **** over and over again...