My fianc'e isn't interested in sex anymore:(?

we've been together for a long time and we love eachother dearly.. the only problem is that i am much much younger than him (that is personal and private i will NOT tell how old he is or myself). i moved in with him last year. we use to have sex a lot because i would visit him on the weekends at first and then go home. we did it like 2 times a day sometimes. once i moved in we had sex atleast every 3 days. after a while it started to be every saturday...now we hardly do it at all and it upsets me because he says it's not the most important thing in the world and i tell him i know that.. it's not.. but it's still part of a relationship and it's only because i love him. he sees it that i ***** at him about it when i ask him why he never wants to have sex with me anymore or when i'm upset he sees it as i'm bitching about it. he tells me it's cause' he's older and it's not as interesting anymore and i just see it as..how can you say that? it make sme feel like i'm not interesting anymore..like i'm not pretty or beautiful anymore. he also says it's just caue' you get use to a person. we have great days together.. we do love eachother and he's a wonderful man but this is a problem because i'm always horny because he never satisfys me anymore. i tell him i wouldn't have to beg if he would make an effort to try but....he wont. i will NEVER cheat no matter what happens but i'm wondering if there is anything... like a secret to making men horny without them even realising how it happened. i can't randomly touch his c*o*c*k because he'll only move it away sometimes but still hold my hand so i wont get upset.. but i do. it use to give him the erection *sighs* i don't have any really sexy clothes and even if i did that it would probably be useless. al lof the tricks i can think of probably wont work and he wont take pills or anything so.. idk guys is there anything i can do? please don't be rude and ignorant because he is a great man and i am a good person