Well, he seems like the type of guys who are flirty with everyone. Well, that's what i think from what you just mentioned about him. Just try to find out if he's serious with you or not.
Hmm red flags up in my experience. Any man that doesn't want to use a "label" to define their relationship is a cause for concern. He could be stringing you along and then drops a bombshell on you an says some BS like "ohh well we never really "OFFICIALLY" dated. Be careful. As for being jealous, that is your insecurity coming through.
As long as you know where you stand in this relationship then you can take measures to protect yourself from getting hurt. I Think you should let it be know you wanna know what his long term plans are for you.
Obviously you agreed with him to this "no label" thing so expect him to do whatever he wants with other girls since you agreed with this no commitment setup. Do yourself a favor leave him and find someone who will not treat you that way.
I dont know what the post was- but all I can say is that don't cheat yourself. Have your values and stick with them- know what you want and what you feel- know that you are very valuable and make it a thing to love yourself before any guy.
Having said that- be honest with him and tell him what is bothering you. I know its scary to do that because sometimes (from my experience) some guys can be emotionally apathetic and just say what they think regardless- but then again guys can also be sweet. Take the risk and talk to him about where he stands- but I wouldn't do it until your emotions calm a bit and you can think what you will say a little better.
Know that even the most beautiful women inside and out have had boy problems.