Neighborhood drug stores have a sperm test you could try.
Hi the only way you are going to know really is by having the test.
if they do the test and find out he has a lot sperm count you could see a naturopath and take some men multivitamins that help sperm count and DNA of his sperm.
Also this is meant in a nice way, his age may also be a factor. Also does he have a clean diet, drink atleast 1.5litres of water a day and do 30 mins of cardio excersize.
even small changes like this might help.
Also don't just focus solely on your husband.
its a good idea for you to look at you health and identify areas you feel you you improve on to to give you both the best chance at conceiving.
Makesure you get onto something like elevit and he goes on menevit( mens multivitamin for conceiving).
fingers crossed for you:-)