Period

So i was told to come in on Day 2 of my cycle to do my baseline ultrasound for IVF. I had a feeling i was going to get my period today so I made sure to put a pad on and I checked around 3 pm if i got it but nothing..and now when i got home from work at 8:30 pm i realized my pad had blood on it. I have to call my clinic to book an appt but they are closed. So my question is, is tomorrow Day 1 or Day 2 of my cycle? Im so confused.