What Causes Delayed Period With Watery Discharge And Nausea?

hello... I have missed my period by a week now, i took a pregnancy test on the day my period was due and it was negative. now for the past 3 days i have had watery brown discharge, this is not normal for me, and there is not alot of discharge. I have been feeling nausea on and off and have a swollen womb. What could it be if the pregnancy test was negative? should i take another test? Me and my husband are trying to concieve. Please help. Thank you :)