When your relationship is becoming problematic and you are "growing apart", one of the most important ways to fix this is to learn how to "connect" again.
One of the books that I often recommend is the 5 love languages. You can find it in your local book store, library or our Self Help Bookstore. Essentially, it is the "language of connection". If you want to "connect" with someone and build a good foundation for your relationship, you need to do the following....
1 Spending quality time with each other
2 Acts of service ie doing things for each other
3 Physical touch ie hugging, kissing or holding hands
4 Word of affirmation ie telling how much you appreciate each other or praising your partner
5 Gift giving ie to buy gifts for them
Now if you can reflect on when you first dated each other, how much of the above did you do. Now reflect on "now", how much are you doing? Knowing this, will hopefully guide you towards a positive change.
You can find out what your predominant love language is by following this link The5lovelanguages.com and complete a short survey.