I have a similar situation in my group; I think most of the time, I'm spoken to too often, and my input is ignored, even to the point of being able to come up with something, and they will ignore me and continue the conversation to the same point and come up with the same thing as I just suggested 2 minutes before.
It's frustrating and discouraging.
You mentioned that the problem is apparently related to the audacity of your character in the conversation (in your comment);
That was also a problem with my previous character 🙁 although it was not as bad as it was stronger, but this one is much quieter, so it's even easier to speak.
I guess you mean that your PR has an effect on this issue. You play your character harder and you get a contribution because you can not be ignored. You play your character quieter, and he is easily overlooked.
I would suggest talking to the whole group about this, in order to find a way to go forward. The rest of the group may begin to get excited about a situation and may often have a "tunnel vision", seeing only their own contribution in the story. They may just play the characters as loud and deaf as they just can not hear you. Anyway, it's something you need to address with the whole group.
Some suggestions on how to handle this could be the use of an object – a spoon, a ball or something of the sort – the person who has the ball is the one who is talking – any other person has to wait for his tower. It's a good management tool that everyone can learn to pay attention to all members of the group.
The important thing to remember is that these games are meant to be fun for everyoneand if the others do not amuse you, something has to change.