hi there, I totally sympathise, but it DOES get better.
My dd is 21 mths now and still doesn't have much of a routine, and much as would have liked some predictability in my life, I learned to accept whatever happened and just 'go with the flow' a bit more. I have accepted that my dd isn't a very 'routine' baby (apparently I wasn't either). Some babies are, some aren't. Either that or people lie!!! But comparing your baby with others (esp when you're so tired) is a form of masochism, don't do it!
I also found it hard to sleep when she slept, as she would only sleep for a short time. For me personally, just a lie down with my eyes closed can make me feel a bit more human.
Just sleep whenever you can and try and work out some time when you get a lie-in or early night, draw on all your support - Mum, friends or DH - this bit is very important.
And try your best not to think about how tired you are, as dwelling on it, makes you feel a hundred times worse.
Just in case you were thinking about doing anything silly, like housework, obviously - DON'T!
I heard that as babies get older, their nervous system develops and so does their sleep (i.e. gets longer and deeper). I found this to be true with my dd.
Hope that you get some rest very soon.