Best friend confessed his love me

So one of my best friends recently went through a break up with a jealous, psychopath girl. And last night he sent me a message saying that he's actually been in love with me the whole time. And I've been seeing/talking to this guy for over a year (complicated story) and he helped me through a lot of shit that went on with me and this guy and now my friend is telling me he loves me , what do I do???!!!