Hi I Am 21 Years Old Male... Its Been 20

Hi i am 21 years old male... its been 20 days
I have a clot near my anal opening and my stool needs very pressure to pass.. my rectum feels full and lower back or tail bone pains..
I feel incomplete bowel.. after some days i found black patches in my stool... and today my whole stool was dark in color at starting doctor said it was hemmorid gave me daflon500 mg tab ... then after that i felt good no more constipation gutclear syrup was also provided.. but after 10 days i saw black stool with some minor blood mixed.. i am scared my stomach doesnt pain that much... but cramps or even inflamtion occurs sometimes.