I need help with my google adwords campagne

I have been using adwords for quite a few years now and self taught-although I have been advised by the adwords team at times , I used to get a lot of business from it at a cost of approx. £50 per month. I am currently now spending up to £150 per month and seem to gain hardly any business from it anymore. I am a layman when it comes to this, which I find, complicated business and would like help on 'AM I WASTING MY MONEY????'