People talking over you

I don't get it. I've dealt with this all my life, half the time I say anything to group of people I'm either completely ignored or get cut off at my first two words. Why does this happen?? Am I doing something for this to happen?? How do I stop it?? Just so annoying and rude and just makes me not want to communicate with them anymore at all.

It's been happening at my new job and today we had a meeting to express any concerns or anything. Everyone took turns. It's my turn and I get two sentences out and everyone cuts me off and starts talking over about something I wasn't even talking about. Just completely changed the subject and ignored what I said. They didn't do this to anyone else.

Afterwards I expressed to my coworker who doesn't treat me like this that it kind of hurt my feelings and just made me feel like I just shouldn't say anything. She felt bad, and brought to one of our bosses who came to talk to me. Guess what happened???? I expressed I was cut off and went to explain what I was trying to say to be.... You guessed it! Cut off and have the exact subject that was brought up when I said something before.

She kept saying I need to feel comfortable saying something, and I was just honested and said why?? To be cut off or ignored?? How it happens all the time. I can't stand up for myself, like she said to, if I'm ignored and wrote off when I try...

Now, I'm just staying to myself. I've been sitting away from people and keeping quiet. Just annoying and hurts. I don't get why this always happens to me. Sorry, just need to get all that out.