My partner has gone off sex !

We were very active before our son was born. We used to have sex a minimum of 3 times a week. We then decided to try for a baby and sometimes this would mean we had sex everyday during my fertile window. We miscarried before becoming pregnant a month later with my son and this made us both slightly fearful of having sex during the pregnancy. After I gave birth things appeared to go back to normal for the first month or so and then since then he just makes excuses not to have sex and if we have then it feels forced. our son is 9 months old now and I can count on 1 hand the amount of times we have had sex in the past 9 months. we've discussed it and he says there is nothing wrong , he is just down with lifes woes work , money etc... But I can't believe that's really affecting him. He is still very loving , kisses me, hugs etc... But our sex life really isn't the same. Any Advice welcome :)