I ended preseason at Silver 5 24lp

I'm current 5-1 in placements have I done enough to secure my hard work from last season because I've heard people have been losing divisions even with positive placement matches(some below the silver 3 average). Is there any truth to these stories or have my 5 wins secured my at least an equal rank to where I ended. I spent all last season climbing up from bronze 5 0lp and i really don't want to be in bronze again. Also if I keep up my current trend and end 8-2 or 9-1 how high could i get??? I think it was my 3rd game I lost and I've heard which game you lose makes a difference. So if anyone can answer any of my questions I'd appreciate it.