Is there a chance im pregnant or is it all in my head?

hi, im 18 and lately i just have a feeling something isnt right! ... i am on the pill birth control and i stopped taking my pill on the 11th of jan for my week break and i started taking my pill again on the 18th (a week after) i then had sex with my boyfriend on the 20th jan .. it is now the 31st jan and for a few days now iv been getting very sore boobs and i am so tired! sometimes feeling a little sick and i have cramping sort of pains in my stomach .. its nearly been 2 week now and i dont even no if its possible to have pregnancy symptoms this early? plus i am on birth control .. i just want to no if this is possible? or anyone experienced this or is it all in my head? .. sorry for the essay but just need a little advice! thanks in advance.