For the last three weeks I've had all the early pregnancy signs, I have taken one test a week or so ago which was negative, but now I have my period a week late could I be pregnant?

Having a period usually indicates your not pregnant. It sounds like you may have just missed a period, this is normal. Was your period the usual flow you would have?

No its not really the usual flow and its usually a lot darker in colour rather than bright red. Why would I be having all the pregnancy symptoms if I'm not pregnant just seems so weird and I feel like crap 24 7 :(

Having a really light period or spotting can mean you might be pregnant. Most period symptoms are extremely similar to early pregnancy symptoms, but you can always test again in a few days, if its negative then ask you doctor for a blood test.

I never get cramps or back pains or feel like crap when I have my period though.

Nearly every single time myself or another woman gets excited or anxious about maybe being pregnant, we end up with pregnancy symptoms. This is called psychosomatic. Your brain can trick your body into thinking something that isn't true.
This can cause your period to be late or even skip it.

Go see your doctor and find out once and for all. Good luck hon