After pitching, the yeast multiply themselves by several times before starting the fermentation process. By that time I just don't feature a typical re-pitch having much impact on the final gravity of the brew because you're only increasing the overall cell count by 5-10% (unless you're repitching on a whole cake). I've never added yeast after the initial pitching, and I've never checked the gravity before at least 10 days have passed, regardless of what the airlock is doing.
It's perfectly normal for things to slow way down after 5 days. Wait 5-7 more days and then take a gravity reading, that's really the only way to know where you're at. The airlock activity really means little with regard to how far along your fermentation is but 5 days is too soon to worry IMO. Trust your yeast, they almost always come through.