Is this guy really in love with me or not?

Met a guy 4 years ago. we stayed friends bc i just came out of divorce, and wasnt ready. i knew he liked me but i didnt know how much. eventually we went seperate ways (on a good note though) 4 years later, this guy has a gf, yet he came to my home to tell me hes in love with me. and that he always has been. I am completely flattered, since hes been declaring this for a cpl months now, i really feel he is genuine and i am ready for a relationship now. HOWEVER, I asked him if you really love me, then you would know who you want to be with and not hold on to your gf for this long. His response was "I just want to take time to get to know you again and regain your trust and take things slow" Sounds like hes being honest but something still seems odd. he even cries and tells me "i love you" but i say "but you have a gf we cant do anything about this" what is he doing??? if he meant it wouldnt he be with me by now? or is he really doing the right thing by taking it slow? but then again the gf........