lil advice first 2 unplanned planning this one it's not going good

Tae
So I'm in a new relationship we've been together 1 yr 7 months I was with my ex for 11 yrs n we have 2 kids together...Me n my current boyfriend are trying to have a baby he has one child..I'm 31 n he is 28 I wanna have my 3rd n last one before 33..He smokes a lot of marijuana n feels he has a low sperm count..He conceived his son while he had stopped...He was also in a long term relationship before me n she never got pregnant..We have been trying for about 6 months n nthn yet..Any tips or thoughts just would like ur opinion