I don't understand why your doctor is not investigating or at least referring you to an oncologist. You definitely should be concerned and need answers. Are you in the US or in a country with limited medical?
If you had a radical removal of the melanoma site I assume they also biopsied the closest lymph nodes for metastasis. If so did they also remove the cancerous lymph node/nodes? Did they judge your melanoma site to be Insitu, meaning no metastasis. I am not up to date as to melanoma treatment drugs if spread.
My husband of 53 years had radical melanoma surgery on his back lower torso 46 years ago. It was judged to be malignant, meaning some of the cells in the melanoma nest had ruptured open and they removed 122 square inches in the area surrounding the melanoma, removing all tissue down to the muscle, then pulling and stitching what they could and then skin grafting an area about the size of a football. He never had the dark color or shape you are evidencing. Evidently they got it all, it hadn't spread past the radical surgery area. He's healthy today at 76, yet has had 2 more surgeries in the last 5 years for melanoma, forehead and behind his ear, both were Insitu, meaning no metastasis.
One surgery was basic Mohs and the other was a Mohs but the nest has tentacles and they had to go deeper, still the cells had not ruptured and were intact and the surgeon was sure it was all removed.
You are not paranoid. Melanoma is nothing to ignore.
Please keep us updated.
Photos of latest Melanoma: removal, 3 weeks later, 2 months later. First scraping showed tenacles leading to melanoma out of the excised section so a second cutting, much deeper removed the rest of the melanoma nest Initially lower section was stitched and the upper area skin grafted. Skin graft healed.