Clonazepam is the best of the benzodiazepines I've taken. That's my opinion, of course.
I'm supposed to take .05 mg once a day @ bedtime, but since I've been taking them for over 25 years, I decided, a few years ago to see what happened if I only took 1/2 pill. It worked out very well, so unbeknown to my Psychiatrist, I'm still only taking 1/2 - so that's only .025 mg.
Your .25 mg twice a day sounds like a very high dose, and you may be over medicated. The most I ever had to take was .10 mg once a day. I've always gone to a Psych. for mental health, not a GP.
I went to WebMD.com to look up side effects, and here's what it said:
Side Effects of Clonazepam
"Drowsiness, dizziness, blurred vision, muscle pain, excessive hair growth or loss, change in sexual desire, weight change, increased saliva production, sore gums, or cough may occur.
Unlikely but serious side effects: slowed breathing, easy bruising/bleeding, unusual eye movements, unusual fatigue, fast/pounding heartbeat, unusual muscle movement, trouble urinating.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist."
It says nothing about loss of concentration, but if you're taking too much, it's a wonder you can think at all! I can tell you, that at .10mg I was very sleepy and kind of "out of it".
I think it might be best if you call your doctor and tell him what's happening.
And YES! Constant anxiety or stress can make a mess of your concentration.
Best of Luck,