Upper Thread
 

When I sew my upper thread is loose. Is this the upper tension? Do I have to change the number or did I do something else wrong? Thanks

Make sure your tension discs are not full of lint. Run a pipe cleaner in there. Then be sure when you thread the machine that the thread is all the way down into the tension discs.

Do you have the same thread in the bobbin? Threads of different weights can cause tension issues. Have you tried completely unthreading the machine and rethreading? For me, that's always the likeliest source of the problem.

To assure the thread gets into the tension disk, when threading the upper thread, have the pressure foot up. This releases the tension disk so the thread can easily between the disks.

After you clean the tension disks, loosen the top tension and tighten the bottom. Use two different colors of thread on a contrasting fabric so you can inspect for balance.

Check to be sure you have threaded the machine correctly.

You won't be able to follow the suggestion to clean between the tension disks on most recent machines because they are inaccessible and out of sight. (This is a pet peeve of mine after years of having access to that basic area of my machines.) It might help if we knew the make and model of your machine.