In a limbo stage in PhD. How to get out of it? I am in the fourth year of my PhD and I am due to complete in four years. My advisor wants 5 journal papers. I have:


One published article. 
Two articles under review with two different journals, one of the articles has previously been rejected 3 times. 
One manuscript being checked by my advisor.
Two more works-in-progress, but I seem to have reached a limbo with these  works. 


Can someone tell me if my progress is bad, average or good?

When I started my PhD, I would give a lot of effort to the work. I
   would keep track of how many hours I am giving to my work, would try
   to make up if the amount of hours dedicated to my work is less.

Recently, for the past 3-4 months, I am unable to feel that
   dedication that I felt earlier. I can see I am working way less, but
   I can't find a way to make myself motivated to work faster and work
   more.

I am feeling helpless. I am feeling very guilty that I am wasting my time. But when I sit with my work, things go blunt, my brain seems to stop working. I really don't know how should I get out of this phase. 

I am failing to get myself motivated to work harder. The interest is dwindling. I wish I worked more hours but I am failing to do so. I want to work harder which I am not able to do now. 

Please help me out here if possible. 

Advisor info: I do all the work, he just checks the grammar. I do not get any technical input from him. If I talk about how low I feel he would just say, " PhD is like this, don't lose hope". The repetition of these lines does not do any good to me.
Scientific work is always a high stakes gamble. You are never guaranteed to succeed and several failures in a row usually result in a quite depressing state when you lose the willingness to try anymore completely. It is nothing unusual. Here are the techniques that I usually employ when getting nowhere for a long time.

1) Step back and relax. Forget about it all for a month at least. Live your life (I hope there are some things you enjoy besides solving problems, working in the lab, and writing papers).

2) Talk to people in your field or go online (to MathOverflow, say) to see what they are working on and have trouble with. If you are not at the very bottom, there will always be a lot of people whom you can help. Boosts your self-confidence quite a bit.

3) Remember that you are under no obligation ("obligation" is not the same as "pressure") to produce anything or to prove to anyone that you are any good. You came to the parallel universe to wonder, explore, and play. So, just do exactly that. Read something funny in your field, ask yourself some "stupid" questions, etc. Just get the feeling that you belong to the scenery around you and can enjoy small streams and hills before trying to cross a big river or to climb a mountain.

4) Look at Hubble telescope images and try to imagine all the distances, times, and energies involved. That puts you with all your worries, ambitions, and desires in the right perspective. Don't care too much about the problems of something as insignificant as one unit in over 7 billion on some God's forgotten planet in the far corner of some minor galaxy, totally dispensable and replaceable any time. Concentrate on the outside world. You can figure out something about it before your time is over, that is the only game really worth playing in serious, and you are totally qualified to participate in it despite the fact that there always will be much stronger players around. 

There are more, but these four work well enough. And, of course, complain about your situation to your friends any time you want. No need to handle everything alone :-)