Need some advice on why does this happen

So Me and my ex been broken up for 9 years now I'm still close with his family him to he was my first love the one took my Virginity it's like every time I'm around him I get so nervous I get butterflies my hands shake heart bounds fast I don't know why I get this feeling every time I'm around him we did go together any idea why I get so nervous I feel like he's a guy I'm crushing on and I just get so nervous/shy around him please help