Airlock activity is a poor measure of fermentation. IMHO every brewer/brewster should get a hydrometer, they are cheap enough and will allow the brewer/brewster to determine what is happening in the brew with greater confidence.
If a hydrometer is not available at the time of brewing then a good rule of thumb is to leave the brew to ferment for (say) 14 days. Most beers are complete in about 10 days (depending on temperature) but waiting some extra days will not hurt the brew.
Bottling beer before it has finish fermenting (and particularly after just a few days) can be dangerous as the bottles may become excessively carbonated and the resulting pressure can "damage" the bottle - to say the least. Even if the bottles withstand the pressure the beer may behave more like champagne and empty itself onto the ceiling when opened.
So best leave the beer to ferment a little longer.