You may be unlikable to girls for a number of reasons. However, the first place you need to look at is in what is going on in your head.
Your mentality is the first step. If you look at yourself as undesirable and unlikable to girls, you will act accordingly and fulfill that belief.
Look back at your history with girls.
Try to recall where you think this began. Was it early on in grade school or later? There is a good chance that there is a history of this. This typically means that the problem doesn’t lie with the girls but in you.
This doesn’t mean that you are a bad guy or even undesirable. It simply means that you should start looking at certain facets of your character and make some changes.