The guy above who is saying its good conversion rate is right, the people who say try different landing page/content etc are idiots.
The conversion rate isn't bad, you need to find away to pay less for leads. Different keywords, different advertising networks. What is your quality score, are you paying what is estimated by google or more?
Did you get 4 conversions for the first 44 clicks then 72 clicks of nothing? Usually thats not much to go on but you could see if theres anything in common between those 4 conversions, location, demographic, time of the day and so on and set you campaign to only target those.