So confused

So my husband and I got married June 3 this year and haven't necessarily been trying for a baby, but we haven't done anything to prevent it. When it happens it happens. I ended up starting my period this month on Friday (sep 1) and ended it the next day (Sunday, sep 2), which is super weird for me considering my periods usually last around 4-5 days. I did take a pregnancy test before I got my period and it said negative but now I'm starting to wonder why my period was so off. Also, I woke up Friday night/Saturday morning around 3 AM with excruciating pain. So I guess my question is is there any way that my "period" could have been anything else but a period? Some people told me it could have been a miscarriage but I feel like I would've known or at least had a positive pregnancy test? Any information would help!! Thanks!