It's tough/dangerous to give advice over these forums, but perhaps try to focus on relaxation and dare I say it, don't try to control your breathing pattern during breath up at first, just normal, calm, regular breaths as needed - regulated by your body's needs, and not your mind's chatter. This way you can get a sense of how your body and mind react during the dive in an "unaltered" state. For example, if you hyperventilated, then that's "altered." You can even increase your breath-up time to 6-8 min for good measure for a dive approaching a max.
If you don't already do this, pulling up and down a line could be useful to get used to depth as a line gives you more control over your speed and a sense of security with a direct link to the surface.
Also, recreational diving without thinking about accomplishing a "number" has helped me improve in the beginning where the focus is on relaxation and enjoyment. It's easy to burn/stress out on depth-oriented line diving I think. Of course all this with a trained buddy and just my two cents.
