Am I bi or is it just a phase?

I play softball and for the past few months I've been especially attracted to one particular girl. We've talked quite a bit and I've known her for a while before this year, and I've thought about what it would be like to be with a girl a few times in the past. Just a couple weeks ago, I learned that she's bi, and ever since I found that out, it was like all of my feelings for her surfaced. When I'm around her I feel the need to impress her and I get jealous when anybody mentions her being with other people or anything. I've never really sat down and thought about me being gay or bi. I've always thought I was straight until recently, and I don't know where to go from here, but I also don't know if I'm bi, or bicurious or if its just a phase...