My Husband Is 31 And I'm 30 Years Old. We

My husband is 31 and I'm 30 years old. We have been married for past one year. First two weeks we used to masturbate daily and then he reduced it to 2-3 times a week. After a month it was once a week. I was a virgin then,so mostly we would have masturabation and only sometimes tried with fingers. I lost my virginity after 5 months of our marriage and we used to have sex rarely. Masturbation used to happen once a week. And since then till date, my sex life is dull. We focused mainly on masturbation till November and after a discussion we started having sex once a week and till date we just have it once a week sometimes. And now most of the times it's happening once in two weeks as my husband doesn't feel the urge to have it quite happen.
I came to know after 6 months of our marriage that at the age of 27, my husband had an affair with a gal for a year and lost his virginity to her. He was quite active at that time as he used to even go for gyming and played games but now ever since he got married he has just stopped any form of physical activity. Now I have started thinking is it because of me, that he might not be attracted to me that he has lost interest in sex, or some other psychological or physiological problem that he doesn't feel like having sex.I would be happy if it takes place everyday. Does he still think about his ex? What can be the reason behind his not feeling the urge to have something that he enjoyed earlier. He even searched on Internet, ways to satisfy a gal, when he was with his ex. So obviously he had interest at that time. I want my sex life to improve. Plz help.