Plateauing my shamanic breathing

[CalmOrNot]

I've been doing shamanic breath work for almost 6 months now. For the past 4 weeks I've noticed that I'm unable to sustain for more than 15 minutes and I'm unable to enter deep states on consciousness. Also I've started to feel blockages in my body and I'm unable to breath past them as they start to contain me and my breath work gets restricted. Has anyone else here experienced the same? It would be great if you could throw some light on it. 

 

Thanks!