My last 2 periods were a week late and only lasted half the time as normal and I also have pregnancy symptoms as I did with past 2 pregnancys but tests show up negative. Could I still be pregnant??

You can still have periods and be pregnant as well as having a 'False Negative' which is just a test coming up negative but being wrong. This is quite rare I might say though.

All I can say is: Yes. You can still be pregnant while on your period and after a negative test.

I hope this helped.

Take care,
Gin.