Hi. I have been doing yoga for over a year now and I still cannot hold a forearm stand.
This is becoming very frustrating for me and I really dont know what to do anymore.
What could be my issue? I don't have enough strenght? I am quite flexible and if I go with feet by a wall and invert my self I can form a perfect 90 degrees angle so I guess it's not a flexibility issue. I got my splits in a less than a month and I could already do most binds and poses like bird of paradise almost immediately. Some poses like fallen angel required a bit more work and I can almost do it properly now but pincha looks IMPOSSIBLE to me and I wanna learn it so bad. Please give me some advices or exercises that could help 
I am feeling quite frustrated
First lesson in yoga is not to get frustrated. Everything comes with practice.
Another point is, yoga much more beyond than getting mastery of postures.