I fear my cancer is back

I was dx with stage 3 melanoma in 1998 and to date have been blessed to have not had a reoccurance but am scared that my cancer might be back, the other night I had an itch on my back , so, I scratched it and knew something was not right, I felt a little lump and it felt "rough", my husband took a picture of the mole so I could see it,  I am thinking my cancer has returned from by the looks of it. I can not be seen by the doctor until May 20th, I am scared! I am not sure if three weeks will make a huge difference, I am trying not to panic but three weeks seems like eternity.

Thank you for listening