There may be a valid reason, but people who are sincerely interested will not
confuse you.

Ask him out if you're interested! For crying out loud this is not difficult people.

Ask him out already, why does the guy have to make the first move. It's 2014, time to get with it.

could come as a result of many things, so don't prejudge. maybe his last relationship was a real let-down/painful and he's slowly working through it - maybe he's just a moody guy, up one day down the next - maybe you're misreading what you perceive as interest on his part... and definitely what @gah said - ask him out if your interested!!! In that respect welcome to a man's world.

your own body language and behaviour.
Most women give off mixed messages

I've talked to many women: they sat there arms crossed,not looking impressed,checking phone,rarely smiling,looking outside,etc so I took that as not being interested.
Then we cross paths and they're all interested... or I hear from their friend that they wanted me to ask them out...

Ditto to what Gah! And Come on said! Ask him out already!!

Guys who want to ask a girl out will ask a girl out. Especially if you said you were flirting.

Get some Lulu Lemon yoga pants.

You will find out why men do the things they do. Just guessing, I think it sounds like he enjoys flirting when he feels like it, but that's all it is. He's not really interested. The art of flirting doesn't seem to exist anymore, maybe that's why women think men are cold and men think women are cold. They don't realize it's just harmless flirting. If he wanted to ask you out, he probably would. He may be too broke to ask you, he may be in a relationship that's going down the crapper, but he's still involved. so many possible reasons for it. I wouldn't ask him out, he's too inconsistant.

sometimes it's nice to have a few people to flirt with and make you smile, but it's tough to keep it in that limbo stage.