When you say you've had your raspberries for 3 years and they're just not growing, do you mean the canes (the actual plant, stem leaves and all) or do you mean that they haven't given you any fruit?
If you've seen no green growth of the plant in 3 years, I'm sorry to say that they are probably dead and it may be best to start again - you have still time to buy some autumn fruiting raspberries, get them in and get fruit this year.
If you are talking about fruit, it may be that you are pruning down summer fruiting raspberry canes at the end of the season which should be left to fruit the next year.