Missed my period and have thick creamy mucus, plus feeling very sick, tired having back ache, but had a negative hpt, could i still be pregnant?

Not likely: Home pregnancy tests are very accurate. They are the same tests used in a doctors office. They can detect a pregnancy 7-10 days after conception. The best time to take one is when you miss your period. If you doubt the result you can repeat it in 1-2 days. If you were pregnant the hormone level would rise enough for detection. Schedule a visit to have your discharge tested.