Is there even any hope at this point?

Getting disheartened, I'm now 4 days late for AF and not showing anything clear on my frers. My boyfriend said that my personality has definitely shifted and he thinks I'm pregnant because I have been all over the place emotionally. I've also been feeling general nausea the past few days.  Someone told me yesterday that since I wasn't showing a line 3 days late that I wasn't. But I really just feel like I am. Is it still possible I am and implanted late? Or am I out?