I am on the pill

I started having sex without a condom about one month ago.. however I am on the pill. I know you can still get pregnant on the pill but I've been on it for about a billion years so I feel like my fertility should have gone down some.. I don't know maybe I'm crazy but the past few days my back has been achy and I have had non stop head aches and nothing will help and I still have my periods regularly.. well I am supposed to have my next one next week but I've also been feeling sick and kind of dizzy and my belly is getting pudgy... I'm not sure if i'm just bloated or pregnant..... my belly usually isn't as low when i get bloated .... I have a very long torso and so from my belly to the edge of my pants is very long and usually starts about my belly button and goes about half way down but this time it's like the edge of my pants getting all of the bloating.. can that change or is it... maybe a baby?