How Would You Know?
It is unlikely that you are going to feel exactly the same way for someone 2 years into a relationship as you did when you first got together. It can be difficult to tell if this is a natural part of lust turning to the comfort and attachment of a long term relationship or if the spark is disappearing all together. To tell if you love him, look deep into your heart and see if you are still willing to put up with his faults and try to help him change (notice I said try, because nobody can force someone to change as that only leads to problems later). If the answer there is 'no', as it sounds like it is, then it is time to cut your losses and move on. It will be better for you and for him. You may feel terribly sad now but remember that it is for the good of each of you in the long run.
Are The Signs There?
I guess there is one thing that I should have brought up at the beginning. Have you ever talked to him about this? Most guys do not see the signs that things are not working. If you find ways of avoiding spending time or having sex with him, or everything that he says and does annoys you - then it is likely that your love for him isn't as strong as it was in the first place. When people say 'Love is Blind' they mean that you don't see someone's faults. So, if you have started to notice them, it would be fair to say that you are falling out of love, but of course, this is a slow process and wont happen over night, which is why it is so hard to tell exactly what your feelings are. A good indicator would also be whether you find other people attractive. If you have started 'window shopping' for other partners, it would definitely be fairer to finish things with your boyfriend.
Communication Is Key
Most couples don't talk when these feelings first start, and maybe if they did, there would be more chance of saving the relationship, then issues are harbored, and get built upon or secrets get buried, then there is no way back.
Maybe you could agree for you to both make more of an effort with each other, or come up with an action plan to make it better, and to sit once a week and see how the plan is going or maybe how the feelings have changed or even the need for different things is. The biggest problem in most relationships is communications. Girls and guys communicate on a totally different level so you need to bring yourselves together on an even plain to talk and don't guess that the other understands.