Does weed cause low sperm count?


So my boyfriend smokes weed, (I hate it but he is trying to stop), he has done it for like 10 years and feels as if it is something he needs in everyday routine, so it’s a little difficult for him to quit cold turkey, but he is trying... now he thinks the reason I’m not pregnant yet is because of all the weed smoking he has done, he heard that it causes low sperm count. Is this true??? I’ve gotten my nexplanon removed in Nov 2018. And every since then we have been TTC. Idk if it’s me or him. Or both of us. Need opinions!