This is an unusual scenario. If you are formally appointed to an external body as a representative of the council, the expectation would be that you are there to speak on behalf of the council. That doesn't prevent you from expressing your own opinions, as long as you make it absolutely clear each time that you are doing so and don't ignore the council's stated views in promoting your own.
If you are not appointed as a representative of the council, as appears to be the case here, you can say whatever you like, but if others present know you to be a member of the council, my advice would be that you still clarify the source of your response each time. In other words, "The parish council has discussed this matter and their view is that... but personally, I feel that..." or "The parish council hasn't discussed this, but personally, I feel that..."
As a final point, I would advise you against contradicting the views of the parish council in a public forum such as this. As a member of the council, you are a part of every decision validly made, whether you voted for or against it, however that doesn't prevent you from reporting the fact that you didn't vote for a motion. i.e. "The council voted to support the proposal to ... although I didn't vote with the majority on that occasion."