Could I be pregnant with periods?

Hi, just wondering how likely it is to bleed if you are pregnant?  If I was 4 months along would my periods have stopped by now ? 
I have had bleeding when I start my placebo tables for 4-5 days with medium bleeding for 5 periods now since I last had intercourse. These periods have not been late, if not two days early... 
But if I was to be pregnant, would this bleeding stop or not be heavy? 
I have heard girls say that they had a period whilst pregnant for like 6 months.. So I'm just curious to know the answer. 
Before anyone says take a test, I have taken two different types first response and clear blue but they were taken at different times a day- never with fmu. All 6 tests have all came back negative as well as one done at my GP.