Marriage sure ain't a guarantee of lifelong happiness, although it looks that way to a couple in love.
Reality sets in and , yes we change , but so what? You can either cry " failure, I made a mistake " or just accept the reality and get on with it. At times that can be a very hard choice ..... living up to your vow. Buu often it is the right one.
For me, marriage was unhappy for years as we struggled to live as dubs, but after my rejection of it and the initial trauma , things got better ( we stopped argueing about it ) Now in senior years we depend on each other and I have to say that she has been great.
So if you stick with it , it might get better, I am glad now that I stayed the course.