Unusually light period

Ladies! Please help!!! So its about my last period. It only lasted a day! With spotting continuing for 4 days. I thought it was strange considering that has never happened before but i thought it was only stress because of having a new job and my husband leaving for a long underway (being gone for 2 and a half months) but as the weeks progress; when my eve app said I'm ovulating, then cramps and nausea started to happen which is again very weirdly for me. I tested twice and the home pregnancy test came back negative (and it was one of those really hcg sensitive one) but I'm still feeling nausea and once threw up in the morning. I am now in my pms stage and been normal except for the cramps and extreme nausea. Please do help... I dont want to make any bad decisions if i am pregnant..