Husband's cougar fantasy destroying marriage.

My husband has an older woman fantasy that could destroy our marriage. He tells me it started from an early sexual experience he had with his friend's mother while they were both intoxicated. He also had a sexual relationship with a much older (20 + years older)co-worker before we met that lasted over a period of months. He would get drunk, call her and they would meet up for sex. He claims that it was only sex. Six months ago he went out drinking when I thought he was at work and he called her while drunk asking to stay at her place. I was at home on maternity leave with our newborn son. Fortunately he was not able to go to her place and instead came home. I discovered what had almost happened and spent the next months reeling from the pain and betrayal and loss of self esteem from this near infidelity while trying to recover physically from the birth of our son. We went to counseling. The mature fantasy didn't really bother me before this happened as I am 5 years older than my husband and thought it a good thing that he liked older women since I was older. However, I am not old enough to fulfill his fantasy of a MUCH older woman.I also came to realize that he had been looking at pictures of her on social media and watching a lot of "mature" and "cougar" pornography while I was pregnant with our son. He had been looking at her face book profile intermittantly throughout our relationship. She was there in the background the whole time. I began to think "What do these women have that I dont have?" " What can I do to fulfill him enough that he wont need this fantasy?". The answer was nothing. I can not make myself older to please him and even if I could he would not want a 50+ year old wife. He rejected sex with me so many times when I wanted to feel reassurance that my husband stilll loved me, even with all the changes in my body that pregnancy was causing, and chose instead to indulge himself in this fantasy and ignore my needs. During the time when I was trying to recover, when I was working so hard to pull my body back together to please him and I felt that I was at my weakest, he tried to cheat on me. I forgave him because I loved him, I did not want to think of my life or my son's life without him and he seemed sincere and resolute not to allow this to happen again. I am still hurting from what almost happened and I still look at myself in the mirror every day trying to find a way to make myself better so that he wont want to think of her or the fantasy that is silently destroying us.
I recently discovered that he has been looking at the mature/cougar pornography again and has been trying to hide it from me. I am trying to give him everything I can think of sexually so that he wont lose himself in that fantasy again. I try to do everything in the bedroom that I know pleases him and I do it very often. I am now below the weight I was when we got together and in really good shape again so I know its not my body. I also know I am looked at by other men very frequently (as my husband has commented on it) so I know I am not unattractive. How can I tell him how much it hurts? How helpless and worthless I feel when he prefers to get off to pornography instead of with me? How I feel like he is cheating on me and hiding it? (I feel that seeking out the fulfillment of sexual needs thru porn is just as much a betrayal as if I fulfilled my needs for attention by flirting with other men online ) How much I fear that he will decide again to try to find a way to make this fantasy real and destroy our family? How every time he closes his eyes during sex now I wonder whose face he is imagining? How seeing that he still prefers to get off to cougar porn rather than having sex with a real woman who loves him brings back all the pain of what he almost did? I feel like he loves his fantasy more than me. I love him so much and want to meet all of his needs sexually but I dont meet the age requirement. I am also worried that as he gets older he may start having a younger women fantasy that I wont be able to meet either. I dont want him to look anywhere else for his needs. I love my husband more than words can say, I just need him to love me enough to not need/want this anymore. How do I make him understand how this affects and hurts us? How ugly and unattractive I feel to him when I see this? How it makes me feel like less of a woman? I have tried to find information online about this particular fantasy but I haven't been able to find anyone with this same problem... :(