Finding work when you have a past

Finding work can be daunting enough for anyone who is unemployed, but when you go for interviews and you get the feeling that you have all the skills required to do the job, you find stumbling blocks. I have had lots of interviews. I know I can do the jobs I applied for but my age and my unsavoury past still keep on rearing their ugly heads. We are told to be open and honest at interviews but it seems that is not entirely the best policy. When I tell people I used to be a drug addict and I have a criminal record and try to show them what I have achieved since then. I am told sorry the vacancy has been filled or they'll let me know and they never do. Now, to add to this my age and what you have is another huge stumbling block. The government say there should be no discrimination because of age, but there is. It is hard enough for anyone who has a past like mine to get work. I understand how a company can find it hard to employ someone with my kind of past, but surely when it can be shown that people have lives that have changed for the better. Is it asking too much for someone to take a chance on them? After all the people that have changed took that chance to be better people.