Actually my first instinct when I read your post is that you are going through the 6 1/2 year itch....My husband and I did this also, and almost exactly at the same age too! It's the time when you are completely settled in and any differences seem to rear up. Many marriages have a hard time at this point too.
I have two seperate comments, both positive and negative for your situation.
The first is that this hump is easily overcome. What my husband and I did was first decide to get married. That spurred a heightened sense of commitment to the relationship. We didn't jump into "marriage" plans, but just acknowledged that we did want to be together. Our actual marriage took its course (we eloped with another couple...it was fun!) I got pregnant at 34 and I'm glad I didn't wait too much longer than that. We've now been together for almost 25 years, and we've had many other ups and downs...many! It will never be perfect, but there were moments of perfection.
Question, when you argue is it belittling? I ask this because it's hard to know how you two are during these spats. If they are just stupid arguments, then that is totally normal. If they are arguments about very specific ideals, philosophies, etc, then that is different. If they are arguments about the same thing each time, then that is something to examine too.
Another question..do you both feel respect for each other? Respect is the glue, much more than love or sex or even like. Does he respect you? Do you respect him?
The more negative aspect is the different lifesytles. Now this is something you need to examine. The fact that you give each other freedom is key. Without that freedom to be individual you would be doomed.
My best friend is very active. The woman is always moving. Physical fitness is her guru. Her husband is exactly the opposite. After 20+ years this is now becoming a big enough issue that she wants to leave him. She sees herself as young and vital and her husband as settled into old age. It's a big dilemma for her because she likes him, but she has lost respect for him. There you go.
You guys are young. My husband and I were quite the party goer's back then too. Believe me, it slows down...especially after kids. To almost a comotose level for some during the early baby stage. You change after kids, a lot! Both of you will.
If a decent structure exists in the relationship, you still enjoy each other the majority of the time, there is respect, there is like, there is sex, there are some common interests, if there is kindness and most importantly laughter and humor, then you are just going through the basic 6 year hump. Don't over analyze, continue to offer each other independence and self actualization and you two will be just fine.
You are just going through the "Is this the person I want to spend the rest of my life with" blues. Been there, seen it, done it.....Should you make it, come back here in 15 years and tell me about the other more complicated crap that is going on. I don't care if you are married to Prince Charming, after 25 years it hasn't been, and never will be perfection.
In the end, your gut will tell you that you would rather jump out the window than to hear his key in the door....that is when it's definitely time to say goodbye.
Molly