How can I start being

[flabbyribs]

I am ashamed to say that I have been VERY easy on discipline with my 8 year old DS and I mean VERY VERY easy. However now he has got to an age where he is answering back and speaking to me horrible sometimes. If I try sending him to his room it doesn't work he only comes back down, grounding him won't work either (he only plays in the back yard anyway) and he is too old for the naughty step. He is my only one but we are TTC with second and need some rules laid down NOW! I know it's probably a little bit late but I am at the end of my tether. I have also threrated to take away his Xbox and other consoles but he just laughs. Yes he has been spoilt and I think it is my fault for doing this.
Sorry if this post sounds long and daft but I need some hints PLEASE!
I might have to lock him in a cage before long. (thats a joke BTW)

Don't threaten it - do it. If you're not going to do it then don't threaten it. (does that make sense...?)

It does make sense I WILL do it. A few weeks ago I brought him in from playing footy and said thats it your grounded for the rest of the day (an 8 year old) then I saw that his friends were having a good time and he was upset so I said oh go on go on out then. I can't help myself but do the opposite. I don't know why really cuz my dad was VERY hard on me (not my sis) and I used to be smacked and things if I done something wrong so I am thinking I am probably soft because I don't want him to hate me for being nasty cuz my dad was nasty too. I do hate him for that. (my dad not son)

You need to tell him what the rules are, and if you need to put them on the wall. Don't wait until he knows there is a new baby to think about as that will give him the focus for the regime change, and you don't want him to 'blame' the baby.

like cornsilk says, follow through if you make a threat. And don't threaten, warn.

Taking toys away should work a treat on an 8 yr old, I would imagine from the episodes of supernanny I've watched

Think more carefully about the sanctions then. Staying in all day isn't reasonable and he'll drive you mad. Talk about his behaviour with him - ask him if he thinks that his behaviour is acceptable.