Ice cream is usually made with eggs, making a custard, and then churning and freezing. Yours is hard because of the liquid content.
Are you using an icecream maker or just putting it in the freezer? If method two are you taking it out every hour and giving it a good old churn either in a blender or food processor beating the begeebers out of it with a wooden spoon? This would help distribute the ice crystals and may make a softer product.
With all home made icecream, you do normally need to let it "ripen" in the fridge before serving, as it doesn't have gelatine and other unspeakable nasties ice cream manufacturers use in commercial products to make it scoopable.
Final tip, get the Nigella Lawson Forever Summer cookbook, I found it remaindered at a car boot sale for ÂŁ3 quid last year, and it has some amazing recipes.