Reading your post made me think these things...
1) How old are you? There's certain ages where there's the "Who am I now?" angst blah thing going on besides just the teen years. It isn't fun, but there's some comfort in knowing it's one of those "stages of the age" thing. I kind of expected it as a teen with the "Who am I now that I'm not a child?" I didn't realize I'd have it at my wedding when I was trying to figure out who I was as "wife." Then again when I had my kid while I figured out who I was as "mother." I'm sure I will go through it again and the bit of advice that helped my perspective was someone who told me not to fret too much.
I'm still ME... "Astrophe" is like the name of the newspaper or book. All these other bits are stories/chapters in there that help make up the whole but it's all me all the time... and the further I go the more I know about my life story. But I can't only get through it but so fast, you know? It is OK to just be in a period of not knowing what is going to happen next. You push on and get to know... just like when reading a book!
2) Are you depressed? Have you looked at the symptoms? You can Google more but here's one place to start
http://www.webmd.com/depression/guid...toms-and-types
If you think you are depressed, make a doc appt.
3) Are you meeting your spiritual needs? And I don't mean church if organized religion isn't your thing. I just mean meeting those needs just like you would try to meet your mental, emotional, social and physical needs. In whatever form your spiritual practice takes -- meditation, yoga, gardening, journal writing, art...
I think people need to find something that feeds their spirit as well as meeting their other needs. I know I neglected this area of my life for a long time and it took me a while to figure that out. All I knew is that I felt something was missing and I felt blah about it.
4) Are you lonely? You mention not being satisfied with the romantic relationship department, but are you getting enough friendship and other social relationships? That could cause some blah -- emotional/social needs not being met and feeling a bit isolated.
Maybe someone else can post more ideas for where the "blah" might be coming from.
Good luck!
hugs,
A.