Lazy sperm :-/

My partner and I have been TTC for 4 months now and in the past I have fallen pregnant very quickly (with my ex husband) but my new partner and love of my life couldn't as his ex wife had PCOS and he had lazy sperm... We are still trying with no avail. Is it possible with lazy sperm. Anyone any advice? I heard something about cough medicine? Please help. It's all we want! X