Periods and pregnant?? Please explain

So I'm not sure if I'm pregnant or not. I have had symptoms but negative tests. I have still been getting my period each month: if I was to be pregnant I would now be 23-24 weeks. I have been to the doctor and they said Iv if had my period and negative hpts I'm not pregnant. But heaps of girls on here say they have bleeding while pregnant. I'm on my period ATM and it's red with small clots as usual. Would you have bleeding like this if you were pregnant??