So I was on the questline given to me by barbas, but I wanted to do something else so I went to my house in Whiterun to have him wait for me there. I left him there, together with Lydia who was already there and went to do some other things. The next time I came home, he wasn't there, Barbas had disappeared, and now whenever I try to tell a companion to follow me, they say "looks like you've already got someone with you."

Anyone got any solution?