Means he is not being responsible about your relationship. Does not mean that he does not like you.
Ask him this...
"What reasons make it okay for you to flirt with other girls while going out with me?"
That question is specifically worded, so make sure you get it right. If he does not give a direct answer, then calmly ask it again. And again if necessary. He will quickly realize on his own that nothing makes it okay to do that. Then he will do one of two things.
1. He will get mad at you.
2. He will realize and appologize.
If he gets mad, ask him if he wants to stay in the relationship.
You'll get a correct answer from him.
If he says no, DUMP him.
If he says yes and is sorry about it, then give him another chance.
Hope that helps.