Questioning what I want

I am happily in a relationship w my best friend (a man). But lately I have been thinking a lot about my ex girlfriend and how much I miss her. We were very serious and together for about 2 years. I got out Bc I am still young and couldn't handle the lifestyle (it's a lot of pressure if you're not ready) and it just makes me question my sexuality or what I want. I love my boyfriend very much and want a future with him sometimes I'm just afraid I'm not letting myself be who I am.