I'm 5 days late and I calculated online and it said I was 4 weeks pregnant I have done a test today and I got a faint negative line could I be pregnant

I wouldn't worry about being five days late. Even sexually in-active girls are sometimes a week late.

If you stress yourself about this, your period may take longer to come, so I would try and distract yourself just for a couple days,

And hopefully, you'll see a clear sign of you not being pregnant. If not, it wouldn't hurt to get a pregnancy test after the next couple days, just to see that dark negative line, since the first was faint.