I think many of us here can appreciate the quandary you have found yourself in; to participate or not participate. It sounds to me as though you have avoided doing so for so long it has become habit forming and thus all that much harder to break out of the cycle.

Perhaps, I realise this might sound rather nutty, practise conversations before hand. I will actually rehearse those conversations I have a hunch are going to come up - even different responses for the possible variations and directions a conversation might take. I used to do this a great deal but I have noticed it needs to happen less and less as my ability to converse with people has become more spontaneous. This might be all the start you need. Give thought too to your body language. What is it communicating? In short, consider what message you would yourself like to hear and how it is conveyed. Put some thoughts then now into your communication and the style you wish to convey. Put then some work into achieving this. Eventually new habits are going to arise out of this. Please believe me when I say you can in fact make improvements that will come easier with time.