In response to your overall question concerning whether you can live in two realities at once...if you are referring to Earth-based physical realities, then the answer is No.

This is because you cannot focus here into two different vibrations at once. Your consciousness can only focus on one thing at a time. Some people claim they can multi-task by having their focus in different places simultaneously, but all they are really doing is switching rapidly.

You can demonstrate this for yourself by trying a little exercise.

Concentrate deeply on your big toe (of either foot). Feel it getting warmer and warmer. Start to feel the tingling sensation in it as blood rushes into it and gently relaxes it. Try and feel your entire consciousness actually moving towards and then settling inside your big toe. It might take you a few minutes before you experience this.

Once you get there, stay there for a minute or two before reading on.

Now that your focus has settled on your big toe, shift your concentration to...the end of your nose.

You should now feel quite a definite shift in your (singular) attention as it moves from your big toe to the end of your nose. No matter how hard you try, you won't be able to focus your attention on the end of your nose and your big toe simultaneously.

So having established now that you cannot live in two physical realities simultaneously because you cannot focus in two different ways simultaneously, we come to the crux of your question which is that you feel uncomfortable about getting too involved with your vision because it feels like a dream world.

From what I've said above, you cannot notice you are in a dream world unless you are focused other than in the dream world. Your attention cannot be in two places at once so you are either in the dream world (and then it isn't a dream) or you are not.

And isn't the only way that this can happen because you are aware you are not yet living in the world that contains your manifestation, but instead you have noticed you are in a world that is simply observing that dream world from time to time? Even the language you are using here of dream world gives away the true vibration - the words dream world imply you know you are not yet in the reality of your manifestation.

So what this comes down to then is the good old manifestation killer of noticing that you don't have what you want yet.

In giving your attention to the lack of what you want, you create the experience of the lack of what you want...it's the Law of Attraction working perfectly again in manifesting a world where the lack of what you want still exists. (The word Manifesting is perhaps a misleading term because it implies a fixed state. What is really happening is that the experience of the lack of what you want is being constantly re-created in every moment to match your vibrational output).

The reason you feel bad when you view this dream world while noticing you are in the non-dream world is because your broader self is actually living with the manifestation in the dream world and your noticing you are not there yet is shifting your attention away from alignment with that broader self. Any form of negative emotion simply represents a difference in focus between your broader self and your physically-focused self.

So where are we so far in this answer?

1. You cannot focus (or "live") in two realities simultaneously
2. Your noticing of two different realities (the dream world and your normal world) implies you are not yet in vibrational harmony with what you are trying to manifest.
3. You noticing that you haven't got what you want yet is actually stopping it (or slowing it down) from manifesting

And so what is the solution to this problem?

Well it's pretty simple really.

Set yourself the goal of only using manifestation processes to feel better about the thing you are trying to manifest, but never to actually manifest it

...or, to put it another way...

Seek your enjoyment of what you want from the envisioning of it in your experience, not the physical manifestation of it

If your only goal is to feel better about something you want, not to physically manifest it, all the resistance to manifesting what you want vanishes immediately. And the three points noted above no longer become relevant.

In any case, you'll find that the enjoyment from actually physically manifesting something is actually rather short-lived.

It is in the pleasure of the vision of what you want that you will gain the most enjoyment, not from the thing itself.

In that last single sentence lies the key to a long, joyful and fulfilling life. :)