It seems like the England games are either sold out or are not on sale to the public yet, At the Twickenham stadium i looking for. Thanks

You can already buy Six Nations tickets on the secondary (ticket exchange) market, as the previous reply indicated. However, I don't think tickets for England's home games (v Ireland and Wales) have been put on general sale yet. They may never go on general sale because the RFU tend to sell tickets through their affiliated schools and rugby clubs first. Remaining tickets are usually then sold to members of the England Rugby Supporters Club, prior to any general sale taking place.

They are.