Confused about this guys intentions! Is he just after one thing or not?

He is a personal trainer at my gym and it started out with him staring at me for over a year at the gym. All he did was watch me intensly whereever I am in the gym and never say anything, sometimes I would turn around and I would catch him staring. Since I felt very awkward around him and realised he spoke to my brother, my brother introduced us.
He then added me on facebook and has been chatting to me. However I find he gives one word answers and he's hard to figure out. I spoke to a girl who knows him and she said generally he is a secretive guy and doesn't talk much. She also told me he has had a girlfriend (not a proper one) during the year and he's a player and gets with many women.
He still stares at me at the gym and seems a little nervous at times.
He recently messaged to say that it's about time I got a man in my life and was asking me what I think of him.
He said he hasn't found the right woman until now, but I don't know if I can trust that he genuinly interested in me or if I'm just another girl to add to his collection?