Drama Similar to Itazura Na Kiss.

the only drama I can think that is similar is Goong, also known as Princess Hours. They live together, they're still in school, it's funny, etc.

The first thing that came to mind for me was the Taiwanese drama Just You. The plots are really different, but there are similarities like the two don't get along at first and they live together but then they grow to like each other. And the whole drama isn't just build up.
Shining Inheritance: again don't get along, the guy is rude at first, and they end up living together. This one takes a bit longer for them to get together because it's a longer drama, but the build up is cute and I think you should give it a shot.
Also, Healer. It's my favorite drama. Again, the plot is different but it's not just build up, and when they do get together they are incredibly coupley and the guy is so clingy and it's so cute.
It's Okay, That's Love is an amazing romance. A must-watch imo.
Some other recommendations where the drama isn't just build up: Oh My Ghost, Pinocchio, You Who Came from the Stars.

Also, there's a Thai version of ItaKiss that just finished airing. It's called Kiss Me. I haven't seen it yet, but I've heard good things.

You seem like my type of person .. i too have exhausted all INK dramas (not watch the thai YET) watch the anime, read the manga (although still too this day annoyed the mangaka died so it was never finished) but i went on the search. Nearest that i got and loved was:

Smile, you (total love hate relationship at the start but progressed as it moved on - cast were fantastic and although a little long, it will keep you entertained at all times. The grandad did a superb job and just loved every minute)