Can i be pregnant. Once in every 10days?

Hi, I have used regular birth control for 2months(august and september). I was sexually active almost every alternate day from the starting of pack 1 to starting of 2nd pack(did not use any other methods except pills in this gap, but did not ejaculate inside). I have stopped using birth control after my second pack (on 31st sept). I got my menses on 6th, 19th and 31st of oct. And also after 6th of september i had contact only once n i have used emergency contraception. I feel stomach bloating, headache and light sickness(never had these before). I have took upt which said negative twice. Can i still be pregnant? And is it okay if i have irregular menses like this once in every 10days? Should i let nature take its course coz i dont want to use any medication. If it is okay and if it seems nothing is wrong, how much time does it take for my menstrual cycle to get back into position(i always had 28days cycle, never had irregular cycles). Please help with this. Thank you.