I am on Lantus and Novalog. I am using the pen needles. My problem is that the last two Lantus pens I have tried using were working fine , until I got down to about 200 to 240 units left in the 250 unit pens and then I could no longer depress the button. What is going on. and how do I rectify this problem. My insurance company will not allow me to get more insulin by the time I run out of my present amount.