Wow.... this is a very difficult situation. You'd be surprised how many others have also had to make the same decision.
So....I encourage you to look at it a bit differently. What do you want for longevity in you life and a marriage? Stability, a family, a nice home, security? Those are not bad things to seek. You will find that very rarely life gives us everything thing we want including the packaging we want it in.
Did you know that most (not all) arranged marriages are successful because the families are seeking compatibility based on much more than sexual interactions. One can fall deeply in love with someone they are not sexually attracted to, initially, because that person does, in fact, fit perfectly in so many other areas important in a marriage. Not advocating for arranged marriages but just pointing out those people come to love each other for the people that they are and not the immediate sexual attraction.
Also, ALL relationships evolve. Every. one. of. them. You may meet the most handsome man you've ever seen and the chemistry is immediate and passionate but if you think two years into a relationship that they same passion crazy, heart-pounding chemistry will still be there you are very much mistaken. Relationships evolve and you grown into them (or out of them).
I went to a wedding recently and the minister was spot on...... he said 'Today is as good as it is going to get. It's not down-hill for from here on out but your relationship will change and it won't always be rosy and romantic.' Then he said the best advice of all, 'Successful relationships are about choice. I choose you today because I have chosen you to be my partner. I choose you because I respect you. I choose you because we laugh and you make me feel good. I choose you because you know me and uplift me". He said being in a successful marriage (relationship) isn't about the chemistry that will fade over time but it is about the choice to be with the person who you love and you have chosen to build a life with....and all that comes along in life..... which supersedes the sexual aspect in the long run.
Sex and chemistry is important. Sometimes you can grow and discover passion and sexual chemistry you didn't know was there before (sometimes it doesn't happen). You have to decide what you want in the long term. The hope and expectation of a relationship that will be brimming with romance and chemistry or the guy who has proven his love for you over and over again. I'm not trying to steer, honestly, but will you find the guy who you have amazing chemistry with who is also faithful, respectful, funny etc.
If not having great sexual chemistry is a deal breaker for you and that is okay, for some people it is a deal breaker, then you need to let this guy go but don't expect he will still be available to you later on. Someone else will want an honorable, honest, hardworking guy.
You are not wrong just think about all possibilities before you break it off. But, if you can never come around to loving him deeply and being happy, satisfied and, yes, proud, that he is your spouse then let him go. You don't want to be upset because you don't want to be walking down that aisle but you find yourself doing that solely out of obligation.
We can't tell you what to do...... this is a decision only you can make.