CD 1 before IVF med injections?

I started light spotting last night and when I woke up this morning to go to the restroom it was the same but after a couple wipes then it turned bright red which excited me so I put on a pad and called the RE to let them know it was my CD 1. Basically since that time, things have gone back to a light brown spotting. Now I’m nervous that it’s not truly CD 1 and I’m supposed to go in super early tomorrow for b/w and ultrasound. Anyone have this happen to them and they were still able to start their injections?