How to tell boyfriend I'm pregnant!

Allison • 28 years old, 2 miscarriages in ‘15 & ‘16. Married 💍. 💙 KJS 6/30/18 💙 BBS 4/29/22
I'm 19 years old and I just found out I'm pregnant today. My boyfriend of 1.5 years doesn't know yet. We weren't actively ttc, and although I already love this little baby, I'm so scared to tell my boyfriend because I don't know what his reaction will be. 
How did you girls tell your S/O that you had a surprise baby on the way?