Boy trouble: Help with texting?

It seems like he is friends with many girls, including me, but I'm the one that likes him. He smiles at me in the hallways, sits next to me and talks to me in class, he "messes with me" in a flirty/funny way. We do text often... but I don't know how often is too much?? I don't know why but Im normally bored on Sundays and I would just text him on Sundays... and I text him sometimes after my lacrosse games, but he will say "Brb hw" and not text back after that.. So I just want to know how much is too much to text him?