Please help? I am confused about my period and i am going on pill?

My period in January started on the 14th and then my period in February started on the 21st .. i dont know if thats normal, but what i want to know is when abouts will my next period come? and can i take my first pill anytime after that period? because i go on holiday on the 8th of july until the 21st and i really dont want to be on then.. Thankssss :) xx