Can't stick to something; specifically religion.

Does anyone else have it where they believe something wholeheartedly for like half the day and then the complete opposite for the other half and not necessarily consecutively? Like Ive been having this debate between Christianity and Islam for the last month or so it seems. I think I need to choose one because I want to grow in a community. I've prayed but ultimately nothing seems to persuade me one way or the other for more than, like I said, half a day. Anyone else know this feel or conquered this problem? Any advice is good thank you!