Hello Jeanne, what insulin are you injecting, is it Lantus or Levemir? If so, these are slow acting insulins that work to counteract the glucose that is slowly being released by your liver throughout the day and night, to keep our body's functioning (heart beating, breathing, etc.). If there is not enough insulin available then this glucose can't be used efficiently and blood sugar levels will climb.
By missing injections you will be reducing the effectiveness of glucose use and will suffer the effects of higher than normal blood sugars. In time this can cause much bigger problems. You won't stop breathing or anything, but your body will not work as well. It's very important that you try and get a system going that will remind you that you have to take your injections and stick to it - perhaps an alarm on your mobile phone or other device, or possibly on your blood testing meter if it has one.