I hope that what I have to say will not veer into medical advice. Hard to know where the line is.
The MRI will be the definitive answer on the stress fracture. I think you're smart to avoid skills until you know.
Whether or not you will be able to continue can only come from you, your parents and your ortho, but if you do have a fracture and eventually continue, I think that doing super bendy stuff would be extremely unwise. As to your question about doing gymnastics pain free - I have seen that go both ways and a lot of it seems to be related to the extent of damage and pain before diagnosis. DD has zero pain, but she'll also probably never do a walkover again. She'll definitely never do a front aerial. Thank heavens for a code with so many options!
Between DD's coaches, me, and the ortho, it's basically been decided that even though she's past the "rest" period from the problem skills, and hasn't had pain since the day of diagnosis we're just not going to go there. Like maybe years down the line she'll attempt them again. As Bogwoppit said, backs are for life, and as her coach said, "Why risk it?"
I hope for your sake that it is just muscular. Please update us.
And just for general info, since I know Chalkbucket comes up in so many searches, DD's ortho said anyone who has back pain continuously or on and off for two weeks time needs to make an appointment! Don't play with your spine. DD's recovery was/is so easy (knock on wood) in large part because we went in SO early. And in another part because her coaches take injuries seriously. Critically important.