(2-part post):
Some areas of the country still can't receive Freeview so, before you do anything else, check here:
http://www.freeview.co.uk/availability
Then speak to your neighbours. The postcode checker states that I can't yet receive Freeview but (just like all of my neighbours) I've actually had it for several years. So ask around, to check on 'reality' rather than 'theory'.
If the postcode finder says you can't get Freeview, and your neighbours are all in agreement, then you'll simply have to wait until the digital changeover. (In the meantime, an additional signal booster will probably allow you to receive analogue BBC2 signals, but not the weaker Channel 5 signals).
If others in your area are getting good Freeview reception then, quite clearly, your aerial isn't up to the job. (It's irrelevant as to whether it was designed for analogue or digital signals. It simply isn't good enough for your needs). Again it's time to ask your neigbours or, at least, to study the roofs of their houses, in order to get an idea of the type of aerial you might need.