Irregular periods. Late after due date.

Hello. On 4th of September I engaged in sexual intercourse after 12-14days i take test and it was negative. Due date of periods was 29 September but i didn't got my periods on that day. Then again after 4-5 days on 4th of October again i take a test and again it was negative. Then i got my periods on 11th October they were 12 days late. Then next month in November periods started on 16th November which was 5 days late and this month in December till now i didn't get my periods last date was 16th November. I want to ask that is there any chance that i am pregnant bcoz after that intercourse i didn't involved again in intercourse. And test was also negative at that time i have taken 2 test that time. Or they are irregular bcoz last 2 months i got my periods but they come late after due date .