No one is going to recommend how much insulin you should be taking. To do that over the Internet with no knowledge of what youre up to every day or other medical issues would be foolish and dangerous.
Can you explain your insulin regime a bit more? Are you carb counting? There is some info in a previous thread from you about how to teach youself about carb counting -
http://www.diabetes.co.uk/forum/threads/carbohydrate-calculating-for-insulin.108397/ - are you doing this now? Cos it reads like you might still be on set doses of novorapid?
Your on a basal bolus regime. The way that is supposed to work is by your basal insulin (your lantus) keepin your blood sugar steady through the day and night when you aren't eating anything. You can do a basal test to see if 20 units of lantus is the right dose for you. Although you say you take about 20, how much does it vary by and what does the variation depend on? Cos lantus isn't that flexible, it takes 2 or 3 days for a change of dose to settle in.
Then your bolus insulin should be used to cover meals. That's what carb counting is for, to help figure out what your insulin to carb ratio is. Bolus insulin can also be used without food to correct high blood sugar, but there needs to be a bit of understanding of what your correction factor is to do that safely.
It does sound like you need to consider more insulin, or at least a better understanding of how to use your insulin. The ideal range to aim for would really be something more like 5-7 or at least under 10, letting your blood sugar stay up in the double figures isn't doing you any favours for the long term and is probably making you feel pretty knackered and grumpy.