Feel awkward and dont know how to deal with it ?

My team leader at work is a male , we get on really well, and have nights out from work , where a good laugh is had by all. He is with a lady 17 years older than him , who spends alot of time away from home at antique shows etc. He asked if we could go for a drink after work as he had somethings on his mind , i said yes,He told how sorry he was to burden me but he cant keep how hes feeling to himself anymore, He basically told me he has feeling for me and cant stop them . I was taken back and told him not to be daft .. Im now left wondering how to deal with this . any advice please.. I do genuinely care for him and we get on great but dont see him as a partner p[lus he already has one