Faint positive! When to call the doc??

Maya • 27yo, married, mama to a perfect lil' boy, and a fur baby <3!
This might be a silly question, but all of this is new to me, and SOO exciting and nerve wrecking at the same time!! I got a faint positive at 15dpo, AF was due 2/28. I know I want to get a blood test to confirm, but I'm not sure when I should call my ob? Do I need to wait a few more days for the line to get darker, or can I call her now?? They'll probably be booked for the next few days anyway😒.. Thanks so much for your input ladies😊!!