There's nothing like being told you're inadequate when you're enjoying a moment. Even thought the intent might come from a warm, heartfelt place, from wanting to share a personal feeling of joy, being told repeatedly by many in multiple tones (gentle encouragement to outright shaming) by so many different people is a statement that the current state of who you are isn't enough.
"When are you going to start seeing someone?"
["When are you going to move in together?"] optional pressure
"When are you going to get married?"
"When are you going to have babies?"
"No, really WHEN are you going to have babies?"
Just before I met the Dude, my life had a lovely comfortable Single Lady About Town groove. My dance card was full, my remote control was my own and life was grand. I was happily looking for someone, but wasn't under any personal pressure to improve my current state of affairs. I was getting a lot of flack from friends/family to NOT be happy with the current state of affairs. I needed to pair bond immediately, I guess.
I developed a handy stock phrase that I still use to this day, "I'm really happy enjoying the moment that I'm in." I'm a planner and a worrier by nature, so any friend close enough to think they could ask any one of those questions, usually backed off.
We have a phased approach when dealing with this as a married couple. Humour - Matter of Fact - Blunt
All statements basically boil down to "This is private and none of your business." Most people back off. Your FIL, though? That's a special case and I wish you the best of luck.