Do you always hang out with the same people? If so, then perhaps you should bring the issue up with someone in the group who you're comfortable with. Perhaps he or she would be able to give your their thoughts on your inability to participate. That's what I did with my group of friends. I became really close friends with one of them, and I had approached her about the very same problem you're facing at the moment. In fact, whenever the group assembles, I'm still among the ones who say the least, but she does help me integrate myself within our circle much better (she makes sure that I'm involved in conversations and all).
The problem may also not be with you, but with the conversation topics put forward. Perhaps you don't intervene because you don't know what else to add to whatever's been already said. This goes for groups you don't normally hang out with as well. Remember, people are always attracted to new, diverse opinions and perspectives on both familiar and unfamiliar subjects. If you have something truly unique to add, people will want to listen. Familiarize yourself with the topics entertained by your group, and read up on them as much as you can and create unique opinions and challenge current ones! Information is power!
If the topics discussed simply don't fit your interests, then you may need to change entourage and put yourself into situations in which you will meet people who match your personality. This can only be done if you've more or less well defined yourself (I still have some work to do in this area myself
).
When introducing new topics, you can't just pick any which one you want. You have to mesh with and adapt to the group. Discover what interests each member and what interests them collectively. Then pursue other topics that they could really get into. There is some trial and error involved, and this is more difficult for groups you've just been thrown into, since this required summing up people you've just met, but somewhere along the line and with practice, you'll get it right! Again, the more well-read you are, the easier it will be.
Basically, my advice involves changing the mentality you go into these situations with. Instead of solely dwelling on why they aren't including you in conversations (I used to do this A LOT), focus on why THEY need you in their group. Of course, interaction is a two-way street, so if you feel you're offering too much and they're offering too little in return, a change of strategy may be required.
Finally, if you intervene and someone interrupts you and attempts to change the course of the conversation, politely interject and state firmly that you aren't quite finished. People will take notice and will realize that you have your place in the discussion. Not easy to do at first!
Don't give up! Trust me, I know exactly what you're going through, and even I'm still working on all this! With perseverance, things will get better!
