Negative pregnancy strips and negative clear blue digital. 4 days late

Hey everyone this is going to sound very strange and I honestly have no idea what is happening right now, but here's the story...

Basically me and my OH decided we wanted to try for another baby. I came off the pill and had a period which lasted my usual 6 days. I then came on on the 21st September which was 31 day cycle. I always used to be a regular 31 day cycle before going on the pill. However this period didn't want to stop I was bleeding for 11 days straight. 

After ttc lots this month I'm now 4 days late. But am I if I was on for 11 days. Would that have messed my body up. Have tried some cheap strips off amazon and all negative and also tried a clear blue digital "not my first wee of the day" and that is also negative. 

Please I'd anyone has any advise reply to me. I really hope I am pregnant but if I am why all the negatives

Mel x