For the past 2 weeks i've been having pain under my right ribs, not very bad pain but just uncomfortable, it seems to be worse when I lay on my side or am sitting down. Has anyone else experienced this or know why this happens??

I read somewhere that it is to do with the baby jabbing you in the ribs and that it eases when the baby engages, releiving pressure from them.
I am not sure when this is supposed to happen, I would have thought in the 3rd tri. I would imagine all your insides are being squished up to make room for the baby adding to the pressure.
I would get it checked out If I was worried though.

I have been having this a lot lately, although its my left side just under my ribs, i thought maybe i over stretched myself at work or carrying my toddler around etc but it could just be how baby is lying/kicking! think its been kicking me too hard in the ribs! lol

It is most probably just gas and heartburn combined. Drink a good dose of Gaviscon and you will see it will be gone the next day. Works for me.

Gaviscon? What is that and where do you get it?

graviscon is something to help heart burn, if you go in your local chemist they should be able to give you something that will help.

I was getting the pain about a week or two and it went away after a day or two, the baby moved so i think it was the baby.

Actually, it could be all those things posted above, but it's most likely to simply be your rib cage expanding. Like how your hips "relax"? Well, your ribs expand to provide more room for baby also. I had some discomfort with this with my first pregnancy. It usually is more of an issue later in the pregnancy, but since you're carrying twins you need more room sooner! Your rib cage will go back to normal after babies come. You might also start to notice that your bra's are getting a little tight around the middle. Same thing! It'll go back to normal later!