Your parents punshied you like that simply for smoking weed?

Where the hell do you live? If my kid is 18 and has never tried weed I'm going to kick his ass. But seriously, there is no reason to stop. Just be more careful. Sounds like you weren't exactly careful to begin with to get caught like that so maybe this is your chance to straighten up and get smarter when it comes to situations like the ones you faced rather poorly.

and I didn't understand any of this:

I told them if they allowed within their house I wouldn't be in this situation anyway, and I told them I'm not going to disobey by smoking within their own house
Don't ever tell your parents to go fuck themselves. Thats some lousy ass advice that would not do anything but get you in even more trouble. What they dont know, dont hurt.. so just keep smoking and dont ever get caught.

You should have just told them you were experimenting and you were depressed over a girlfriend breakup or something and that you didn't really like it and will never do it again.