How do i get my relationship back to the way it used to be?

Me and my girlfriend have been dating for almost a year and a half now. Everything seemed so perfect! We discussed our futures together laughed all the time and couldn't spend enough time together. Now things are slowly going down hill. We seem to fuss more and more and we have hard times compromising. Thee is no more talk of the future and I feel as though she deliberately plans over top of our plans so she doesn't have to spend time with me. How do I get that spark back that she once had for me? I love this girl with all my heart and have thought many times about putting a ring on her finger... now I keep debating whether or not I should just break up with her so we can just move in our own directions... someone please give me some advice!