Does masturbation affect sperm quality

My SO masturbates a lot, like a looootttt. Twice daily almost everyday even on days we have sex which is a lot as well(4 time a week sometimes more), I've caught him. in the dead of the night doing it... i don't mind most times cos at least, hey, hes not cheating but if it's coming between me and getting pregnant, i mind like a whole lot. cis we have been ttc since i miscarried in 2015. Does it affect it and how do i get him to stop. Please advice me...

Thank you