<human>: Can you give me the gist of the text in a nutshell?

So I've dated a bunch but never had a really serious relationship in my life. This was my first. It was love at first sight, thought I was going to marry her, etc. Unfortunately I messed things up, know what I did wrong and am going to have to improve in the future. 

Unfortunately, I've never felt this awful in my life. All I do is think about her all the time. Everything seems to remind me of her. I've gone no contact, and it has been crazy terrible. It's amazing that only 4 months with someone can do this to me. 

We broke up a couple of weeks ago. I went on a date last night at the urging of some friends. It was fine. She was very nice, and we had fun, but all I did was think about my ex the entire time. I feel really bad for the girl I went on a date with and I was straight up with her afterwards. 

So my question is this. How do you know when it's okay to start dating again. Does there come a time when you think about your ex and just don't hurt anymore? I think I was trying to do something to fill in the hole in my life. 

Any thoughts are appreciated.
<bot>: Broke up a couple of weeks ago. Went on a date, knew I wasn't ready almost immediately. How do you know when you are ready?