I have a new site that I've been doing a lot of link building for. The ranking was going down slowly over the course of a month. Then in one day it goes from #18 to #5. It stays at #5 for about 2 hours, then jumps back to #18. The next day around the same time, it drops to #7 for about 2 hours, now back #18. What's going on with this ranking?