My Facebook Page Reach Is Going Down... HELP

I have started a facebook page last month and when it has 2K likes , it had amazing engagements and reach. Actually I got 100-200 likes per post when I have 2 K likes. had 20-50 shares too.
But ,from few weeks I don't get enough reach. I have 5 K likes now. But the reason is , I get only 10 15 like for a post and very low reach. My reach becomes declining day by day .I didnt boost still. But I implemented everything that I can do. Please HELP ME !!!!!!!!!!!!!!!!!!

They probably want you to spend on ads so they can make money. As far as I know, that's the only way to "fix" it.