This is interesting to me because it sounds similar to an unfortunate dynamic that developed between me and a former sub, although you sound like you have a deeper level of commitment with this person than we did.

That being said, I have a variable work schedule and I travel often for my job. Some days I work 12-14 hour days, there are often times I'm out of cell phone range much less near an internet connection. Then there are days I'm working from home and can spend more time chatting, IM, etc. In any case, the lack of contact produced similar feelings in my sub, especially since it probably seemed to not have a clear pattern from her perspective.

If there were any signs of attention from other subs (even if it was online, such as friend requests) this simply exasperated the situation.

She often had the same feeling you did:
i would rather let Him go now before we get even farther down the path because i think the pain would be insurmountable if this occurred after investing more of myself in Him.
She would then write me messages telling me as much, and she would go on about how she knew I had found somebody else, etc. Which couldn't have been further from the truth.

I feel like I'm rambling now, so I'll get straight to the point: don't make assumptions and act on them. As others have told you, have frank discussions and learn the facts about what is going on. Then come to an understanding about what is needed in terms of the level of communication even when one of you are busy.

When my sub continually assumed I was ignoring her for a new found plaything I began to think it was HER way of hinting that she no longer wanted ME around. I learned that this wasn't the case after having several conversations but it put a strain on our relationship and definitely put doubts in my head when they weren't there before.

My solution to the problem of my hectic schedule was to simply tell her exactly what was going on with as much advance as I could give. I would say when I wasn't going to be able to have access to the internet/phone and why. I would also make sure to tell her when I thought I'd be back online, so to speak, and I would contact her as soon as I could. On a side note, I would also give her tasks to do while I was gone to try and remind her that even though I was temporarily physically gone, she was still mine.

You've gotten excellent advice from others here and this message is already very lengthy, so I'll end it here. But I thought I'd give a perspective from someone who's been on the other side of a similar relationship.

Good luck, I hope this gets resolved.