Hay, I feel you, super stressful yan, lalo na when the symptoms keep going but walang clarity pa. A few of us mums have been through delayed periods with negative tests, and honestly it can happen for so many reasons, stress, hormonal shifts, kahit exercise changes pa lang, so hindi mo dapat mag-worry too much right now. The heaviness, back pain, and that feeling na parang lalapit na ang period is actually pretty common signs, pero since you're 6 days late na at may persistent symptoms, it's really best to check in with your OB para they can do a proper evaluation and blood work if needed, sometimes the timing of tests matter, or there's something else going on na kailangan i-rule out. In the meantime, rest muna as much as you can, drink lots of water, at try to stay calm, your body's just being unpredictable right now, pero you'll get answers soon!