Should I go off LMP or ovulate date?

Nicole
My LMP was April 11th, which would put me at 5w4d, but I tracked my BBT and ovulation occurred April 28th, so that would technically put me at 5w1d, correct? 
I go for an early ultrasound on Wednesday due to a previous MC, which would be 6w2d from LMP, or 5w6d from ovulation. I'm just anxious to know if I'll be able to see a heartbeat since my days are a few days off. I previously MC at 6 weeks but didn't find out until almost 9 weeks, so this early ultrasound is very important to me.