how to bounce back in bed?

So my Sex life with my so has dried up to about once a month with my nagging and then ending up with very short sex that feels forced like he is just trying to get the job over and done with so he doesn't have to be doing it. Ever since I got pregnant he just wanted it less and less now we have a 7 mth old and it's almost completely non existent. He makes excuse to tired from work not in the mood that sort of thing I know he's not cheating. Just wondering if there's anyone who's had this happen with the partners and how you jump started your sex life did you both see a therapist?