Probably your website isn't designed for conversions. It's one thing to rank and another to convert. 

You would be wiser in spending your money on optimizing your website and getting free traffic than trapping yourself into advertising. What happens when no one buys your service and you run out of your advertising budget? You totally disappear and take a complete loss.

Ranking organically takes time but sticks, in the long run, bringing in constant free traffic after the initial investment.

Advertising is a great supplement for a converting website or landing page but very risky if that is what you are relying on for traffic.

What is your website address? I can take a look and give you some suggestions.

P.S. Are you using analytics? That alone can paint a clear picture.