I.
I thought he was swimming - I thought he swam for a while but found out it was a lie
I thought he is swimming - I thought he was swimming now, but he's not.
I thought he swam - I thought he once swam (don't know when).
I thought he has swam - I thought he has already swum recently (a couple of minutes ago).
I thought he had swam - I thought he had already swum recently (a couple of hours ago).
I thought he ... but i changed my mind, and now i dont think in this way
If I can't frame my thoughts in this way, how should I do it? Specify proposals, add new ones? But is it possible to designate meaning with the help of time?