It depends when you say it, for example , you can say after a big meal " I'm bursting! I can't eat another thing!" If you have had a lot to drink, you can say, "Where is the WC? I am bursting!"

Thank you:)!

It can mean many things. Yes, it can mean I really need the toilet. It can also mean I have eaten too much food. It can also mean that I am very excited about something. It depends on the context.