I understand your problem because I've been through it before, so I'll be happy to answer your question. Usually if your friends with a male since early childhood, you'll seem like a sister to them. And as they get older they start pursuing other girls, and push the 'sibling figure' away. It happens normally, and if he gets a girlfriend that's not the jealous type, he'll probably stop ignoring you and talk to you.
Also, a good way to converse with him, would be giving advice on females from a girl's perspective-If he asks, though that isn't quite common if he's got pride.
Hope this helps~!
Greed Avaricious