If the medication doesn’t work what do I do?

Hey guys!! So I haven’t had my period in 3 months. I went to a doctor who prescribed me medroxyprofesterone acetate and told me to take them for 10 days and my period should start shortly after. So today is my last day taking them and I was just thinking... what if they don’t work? The doctor told me to come in immediately if I still didn’t get my period, but I moved a couple days after the appointment and don’t currently have a doctor at my new location. Has anyone taken this before and does anyone know how serious it is if they don’t work??? And how long do I wait before I freak out if they don’t?? Is it emergency room level bad or is it just like... go in when I can kind of thing?

Any info helps! Thanks!!