Shell, my first thought would be to add Herceptin back into the mix. Of course, you'd have to drop out of the trial, but I assume you're going to be doing that anyway with progression and needing to add or switch chemo's.
I'm on a combination of Herceptin/Navelbine/Xeloda for stubborn mets to the lymph system, and since adding Xeloda last month we've seen measurable improvement as opposed to stable disease. This is a departure for me, as for each of three recurrences to these same nodes since 2001, we've used just Navelbine with Herceptin with good results. My onc felt that since I had good responses with Navelbine, and periods of either remission or stable disease in between while on Herceptin alone, that Navelbine was still a good option for me, and he has been right on.
Although you had Navelbine previously, I'm assuming from your post that you had recurrence some time after finishing, so Navelbine/Herceptin (considered quite synergistic together) may still be an option for you if you didn't progress while ON Navelbine. Also, Navelbine is considered very effective against lung mets.
I hope some others post with their treatment decisions, as I'm sure you're worried and anxious to put together a plan. Hang in there, you DO have many options still, and I would hope one of them is still Herceptin
<3 Lolly