Change can be quick

I woke up this morning with a scary realization... things in a relationship, feelings and such... can change so quick... in less than a week...
I woke up so sad this morning realizing that things are changing. Its only been 3 months, and I can already see things changing.
More and more everyday, I feel less and less like a girlfriend.
We used to see each other almost every day. Or at least every other day... now its a couple days before we see each other, and he makes no move to come and see me... and honestly I dont either. I have learned with him not to make plans with him becuase something always seems to come up. But it just feels like I am not an importance to him like I used to be.
Is this normal? I have never worried before if a boyfriend wants me as his girlfriend.. Yea I have worried about if a man is cheating on me... but I am not really worried about that with him... just that I am not right for him...
Is this normal? Is this a normal part of a relationship? Maybe he's just getting tired of me? And maybe I am just over analyzing the whole thing and theres nothing even wrong...
maybe its just me.