I'm acc terrible at maths. I don't know anything in maths from first year until now ( 3rd yr ). Is there any point on studying maths because I know I'm going to fail haha. Will it affect my subjects for leaving cert if I fail maths ?
The junior cert won't count for leaving cert at all, but try do some exam papers. It doesn't matter what you get in the junior cert, it's leaving cert that counts
And you have the whole year to pick up stuff
Usually, if you fail to at least pass a subject at HL in the JC, your teacher won't let you continue doing that subject at HL and will advise you to drop to OL. Seeing as you put OL in the title of your post, I'm assuming you're already doing OL, in which case I think your teacher might advise you to drop down to foundation level for the LC if you fail. This mightn't seem so bad now, since only your best 6 subjects are counted for Leaving Cert anyway, but it might come back to haunt you when you're thinking about university. Most universities do require a pass in OL or HL maths, except for a few courses relating to Arts and stuff like that, so you should really consider this.
But you don't have to be scared by that, because it's only September and there's still time before your Junior Cert! Even if you think you're not able to get a good grade in maths, have a positive attitude and work hard by listening in class, doing your homework well and revising and practising exam papers. If you find something difficult, ask ask ask and practise practise practise until you get it. This probably sounds like a crazy rant, but it's still possible for you to raise your grade and pass maths. Don't give up!