-snip- I was thinking that I may have made the transactions and forgot, but it looks like the bitcoin has been split into multiple accounts which definitely was not me, so I guess that is stolen somehow
That "split" seems normal, the last transaction just spent the change of your previous transactions, plus one that's probably from your older transactions.If it's really not you, then the issue must be there's someone else who've used your seed and passphrase combination to make a wallet because why would a hacker send coins to his victim's wallet
I bet this is just caused by a cloudy memory.