My sperm is weak what should I do to make it strong?
Make a sperm count test along with a "motility" test (very important). If the count is in the range of > 20 000 000 per 1 ml of semen you are on the safe side. However, from these 20 million count only one sperm is needed to fertile the woman's egg. The journey to the egg is what matter and this is measured by the motility ((example, 50% motility means that you have a chance of 50% of your original count say 20,000,000 ==> 0.5*20,000,000 = 10,000,000 of your sperm count will have the ability to reach the egg and the other half will die in their journey)). Therefore the lower the count affects the possibility and this goes in correlation with the motility.
If a man builds up sperm for at least 3 days without ejaculating it, when he does finally ejaculate after a base amount of time as 3 days healthy men should ejaculate 2 tablespoons of sperm as an approximate minimum on average.