This world is like ours but time travel is possible.
The character and others have made time travelling in their past to change things but did not think about the consequences, so they created multiple timelines without realizing it. The parallel universes are quite similar to my character's own universe. Some "minor" changes are for example that his wife is not his wife in another universe, but became an enemy, and some of his friends havent died, and so on.
One day the character starts to feel as if he had very different memories while still having his own. Sometimes these memories get quite real like he sees his wife as someone who always hated him and married his childhood enemy, sees the ones who died in person and remembers how they never died, but then realizes that they actually did. So he is torn apart between the two timelines. He also meets people who shouldn't have born in his universe. Nobody believes him until his other fellow time travellers start to see these too.
So can these timelines affect the "real" timeline this way? Can these parallel universes collide? At least in their minds? What would be a "scientific" explanation for it?