When did you say "I love you"?

When did you or your SO drop the bomb? 
My boyfriend just told me on v-day (I couldn't say it back). 
I felt like it was too sudden. 
It's been a little less than a month. 
And having him say it this early on in our relationship has me freaking out. Like maybe he isn't taking it as seriously as I am, or maybe he thinks we're more serious than I thought we were? 
He's understating of me not saying it back, but I'm feeling insecure now. 
Has anyone else been in this situation?