Please help!

Hello! I started Provera on March 25th, ended it on April 3rd and my period started April 8th but, my period only lasted a couple hours on CD 1 and then started back up and lasted only a few hours on CD 2 and stopped late on CD 2 and hasn't started back up and I'm supposed to be on CD 3 and start Letrozole today. I called and messaged my Dr. but no response and they're closed now. Could I start Letrozole tonight still? It's April 10th. I'm supposed to take Letrozole from CD 3 to CD 7. If I don't get any answers soon, I'll just start it and hopefully I'll get a call or message back from my Dr. tomorrow. Do any of you have experience with this? I don't normally have short periods. They're medium flow these past 2 days and no flow today. I normally have heavy flow for up to 7 days. Last 3 cycles they were up to 5 days. I didn't have a period for 3 years before the last 3 cycles. Sorry for the long explanation of what's going on with me. I figured the more info the better. TIA for any and all help.