How long has it been since the company was founded?
I assume the company existed for several years before you bought in, so that the age of the company is more than 6 years. According to an interview with VC investor Marc Andreessen, VC is taking longer to IPO (12-15 years, I think).
When private investors buy shares, that "funding round" determines the price/share for the company stock. You can search for "<company> funding round" to see what public information exists.
Over the past 6 years, your stock has grown +17%/year. During that same time in public markets, micro-cap stocks have gained less than 5%/year, and small caps +8%/year. I've heard of this difference called a "liquidity premium", where you earn a higher return for being willing to hold shares long term.
Before you decide to sell or not, read up on the "start-up J curve". Early on, the stock valuation can go nowhere or even drop. In the later years, the growth can be explosive. If you wait for those later years, it might be painful to see the stock grow very quickly after you sell. Keep in mind selling has a risk of FOMO.