How would I be able to tell it is skin cancer aside from going to the doctor, is there any home self test or something?

The Ugly Duckling. Interestingly, the "ugly duckling phenomenon" is very helpful in identifying potentially dangerous lesions. Essentially, if one lesion looks oddly different than the others it should be taken into more close consideration.
A few clues. There a different types of skin cancers some are easy to diagnose by their clinical appearance, others require a trained eye (dermatologist). Regardless, all need a biopsy to make the diagnosis. I recommend that you go to the skin cancer foundation website (www.Skincancer.Org) to learn more. The website is a trusted resource with photos & helpful info. If you are concerned see a dermatologist!
Look in the mirror. Examine your skin regularly. Look for spots which are changing in size or color. Also look for spots bleeding or ulcerating. If you see any, make sure to get them checked out. If you have a strong family history of skin cancer, see a dermatologist early. Lesions are suspicious for melanoma if they have (abcd): a-asymmtry, b-irregular borders, c-different colors, d-diameter >6mm. Best wishes.
ABCD's. Remember your abcd's when thinking of melanoma. Look for moles with asymmetry boarders that are irregular color differences within the same mole diameter greater than 6mm also any new mole or old that starts to itch, bleed or ulcerate should be of concern. Another rule is the ugly duckling rule. Which refers to a mole that looks distantly different from the others on your body.