UHH my best friend loves me WHAT DO I DO????

Ok so my best friend and I were talking about our sad sad past relationships and all of a sudden he dropped an “I love you”. Well it was more like an “I’ve kept this hidden for a while now but I love you” STILL I was confused???? Like hello??? You have A GIRLFRIEND WDYM YOU LIKE ME?? Σ(っ°Д °;)っ ok a bit more context ;-; yes he does have a girlfriend but their relationship is rocky ;-; Him and I have been friends for about 5 months now and we practically know everything about each other. He’s always been a touchy person but overall a kind and affectionate person so I’ve always thought that he would never harbor any feelings towards me.

So I asked him like do you like me platonically or romantically? He said romantically. But I don’t feel the same way so I don’t know what to do because I don’t want to ruin this friendship we have (￣∇￣")