People's feelings change all the time, we are fluid things, even in a stable relationship where you love each other there are moment of greater and lesser closeness, more or less communication, anger, upset, joy and sadness which leads to people behaving differently. It can be long term or short term, or increase over time and lead to serious changes in the nature of the relationship, but it's really hard to judge if you're not there at the time. If you are not that into him then not sure why you are worried, tons of time, so just relax and enjoy yourself x