I am being sued for a supposed loan in 1996

I was very good friends with this my ex husbands nephew (we are close in age) and I had lent him money for things such as clothing, starting up his business and also a trip to Cancun with my daughter and myself. Now after all these years he is losing his house and needs money and is suing ME for money that he was was paying me back with. He gave me checks and I didn't think at the time to write what they were for. So now he says I owed HIM the money! I am just beside myself and do not know what to do! I only have 35 days from the date (Aug 28th) to reply and I am sick thinking that he may win since I have no proof that I let him use my credit cards and paid for a vacation and that in 1994 that he was paying me back for! Help! Thank you, Carol A De Pinto