How do I tell my dad?

I lost my virginity to my boyfriend (he's older than me). I'm 15 and my dad wanted me to wait until I was 16 to have sex. Things happened and I didn't. My mother has absolutely nothing to do with me or my older brother. I was going to tell my brother first, as I feel he would take it a little better. But I'm not sure. I have severe anxiety and have panic attacks over everything. I was gonna just text my dad or brother during school and tell them but I'm not sure anymore. Any one else have tough parents? Suggestions on how to break it to them?