Sour smelling, brown/red spotting, 1st trimester

7 weeks pregnant. Got a positive test at 5 weeks. Been spotting on and off since I found out...pink then brown and recently red to brown again. I noticed today a sour smell to the brown spotting. What could it be?! Don’t have my first appointment til May 12th...9 days. I called about the spotting and they said as long as I wasn’t filling pads or having major cramps then I shouldn’t worry.