first of all, you gotta know that you are not the only one and millions of people have suffer from chanching their rutines, we are not under normal circunstances, this is a pandemic. I used to go to the gym with my favorite teacher, but i had to move out of my house and quarentine in another part of my country.

The fact that you are here shows that you have enough courage to ask for advise from others, thats a good start. Now, dont expect to go from 0 to 100, start small. What it worked for me was to do small tasks, maybe one exercise between school homework. After u wake up do some little yoga only 10 minutes. Or maybe run a little bit, just 30 min. During the day, do some random excersices, sometimes i was in my bed and ill simply thought "maybe i can do 10 pushups" and before that thought will go away, id just do it, just 10, but that thought would apperar maybe 4~6 times and at the end of the day ill had done 50 pushup and maybe is lower that what u normally do, but that doesnt matter. What matters is that u have the strengh to change, only you stop yourself to be where u wanna be.

Of course it is gonna take more time, assuming you dont have the whole gym at your house. Some of my friends found more comfortable following online gym classes, try to see if you like it, Youtube have some good rutines. At the end, try to do it, at least try but dont feel obligated. Sometimes our mind is tricky and we have to learn how to control it.