Conversion of your clan to Christianity means only a few things- first, that is the religion you will be converting to providing no other factors are in play. Being of aa particular religion means that the settlements gains a small bonus to converting to it. Other religious structures and the presence of religious agents for that religion will be the bulk of tbe conversion force. Adjacent province's religion can also affect your religion percentage.
Which brings me to the second point: Your provinces have a high Buddhist/ Ikko religious percentage, and that is likely due to having converted early. 70% of your population in a particular province is not Christian, so that is a significant penalty to happiness. Obviously this means you must convert more of them towards Christianity in order for the penalty to disappear. This requires building religious strictures (church and Nanban Trade Port/ Quarter), other happiness buildings like Sake Den; religious agents trainable by building churches are also mobile conversion platforms- the agent is called a Missionary. You can only train a maximum of five per campaign, so you should have at least five churches built as soon you convert to Christianity.
So in short, the reason your provinces are revolting is because you have not been converting them to Christianity. As long as you are not converting them they will keep revolting. Build churches and train missionaries. In the meantime you will have to halt all other efforts and consolidate yourself.