whats the chance?

I have been taking the pill since i was 16 (now 21) so for quite a while, but recently through my own stupidity i havent been so good with taking it on time etc and taking it later than i should be, recently i have been feeling tired, had awful headaches that no painkillers seem to be able to get rid of, a really bloated feeling which makes my stomach feel tender and with a slight ‘ache’ and last few days been feeling quite sick and dizzy, how much of a chance is there that i could of gotten pregnant? i have a long term partner so its not just been a one off.