Q&A Was His Infidelity Based on Me Not Being Who He Wants?

Hi Rick. I am 4 months from discovery. My husband had a 6 month affair with his brothers 2 year girlfriend. I noticed some type of attraction from his part with this 21 year old woman. My husband is 39 yrs old, I am 33. He said they texted and talked over the phone most of the day. He broke his brother’s trust and mine to betray us both to be with this woman. I was 3 months pregnant at the beginning of his affair, we weren't sexually active since I was 2 months pregnant. Spent 3 nights with her at a hotel, had sex with her after 3 months into the relationship. Before we married he had an ex-girlfriend with similarities to this affair partner. The dark skin, thin, divorced parents, and both live in trailer parks. I feel as if though I have never been what he wants or likes physically. We've been married for 14 years and have 2 children. He says he loves me. The first 5 years of our marriage he cheated on me continuously. After our son was born he said he didn’t cheat for 8 years until now. I never met any of the previous affair partners. I feel he chose me for the mother of his children and good wife. Yet he desires other kind of women. How do I know if he is truly in love with me or is only with me for security and children? What if I'm not what he wants?