What Causes Anal Bleeding?

for thes past few days ive gone to the bathroom and when i have to go #2 ive been bleeding, not in the stool, but the whole toilet bowl turns bright red and it shows when i wipe. this morning i woke up and it felt like i had to go but when i pushed i bled quite a bit but nothing came out, i felt pressure so i continued to push but nothing but blood and air. in efforts to get things moving i stood up, when i did a fairly decent sized clot fell out, about the size of 5 quarters stacked on top of each other, which made me more alarmed, and i look down to see a trickle of blood running down my legs.