Pregnant?

I'm Now 22 Days Late On My Period I Took One Test At 6 Days AND It Was Negative AND One At Day 10 That One Was Negative AND Another At Day 15 AND It Was negative. Should I take another one? I have been experiencing some nausea and heartburn as well. Is there any other pregnancy symptoms I should know about.

Update : I Have Now Taken Two Clear Blue Digital Test AND THEY Were Both Not Pregnant , What To Do now