Is your period extremely light / almost nonexistent on the pill?

Ever since going on the pill 2 years ago my period has been lighter than it was. However 3 periods ago I noticed it got even lighter, then I had unprotected sex. Then my next period was a lot lighter than normal and then my most recent period (last week) was almost nonexistent. But I had bad PMS and was super bloated like I usually get. Is this normal? Doesn't anyone else's flow change?