The links you are getting are probably of low quality. To the OP, the number of links per week which you should get would depend on how many backlinks you already have. If you have 1000 backlinks, then getting 100 links every month would seem natural. If you only have 300 backlinks, then 30-50 links every month would probably be best.
Good links, good quality, good sites and lots of patience and hardwork is the answer. It always seem that it takes for every, but if you keeping going at it you'll see a positive result.
dont overload with backlinks and if you do use backlinks make sure they are related to your website.. otherwise big g will kick you off!!
i think for safely, build back link not in one time in aweek, but everyday and not more 5 backlink per day