How do I tell my mom I think I have depression? I feel a bit uncomfortable and worry she may not understand me or believe me.

sit with her in a place where no one disturbs you, explain her about what is depression and how it feels, explain how things are with you, how you feel being in that state, if you can, take her to your therapist so the professional person can explain her more particularly about your situation, plus also tell her how you want her to behave to keep your self away from the feeling of depression, take her help in your medications and if she understand it, request her to help you to come out from it. this could be beautiful journey to new world