Multiple "top prospects"

A little background first, in June my ex broke up with me because the "distance" was to hard on him and he wasn't happy, even though I sat in almost three hours of traffic to be at his graduation, two days before he broke up with me. 
I recently connected with a guy I went to high school with and we've been talking off and on for a little while now. We've hung out and had fun together, but he has some issues and when he's dealing with stuff, cuts me out. So I took it as he doesn't want to be with me. 
I made a few dating sites (plenty of fish, okcupid, tinder) and was having fun meeting guys and just having genuine conversations. Well, I have since deleted all of them because I am now stuck with 5 guys who all have great potential to be more then friends, including the guy from high school. I never thought I would by in this situation. 
I guess the point of this post is to figure what other ladies who either have been in this situation or know someone who has, what would you do? Would you tell the guys "hey just so you know, I am talking to other people to see what's out there " (or a better phrase) or just leave it alone and see who fizzles out?