for what it's worth, i've run into the same thing occasionally. originally i was freaked out, like terrified. i'm not supposed to look into a toilet and see that ever. i had significant amount of blood with no pain though (for a few days in a row). i built up the confidence to head to the doctor on campus an get checked out. i figured if i'm bleeding i should stop being immature about it and get checked out asap.
after describing the situation to the doctor, he just said it was likely hemorrhoids or anal fissures -- both of which can occur with absolutely no pain. i guess i had always assumed things like that would be painful and ruled them out as possibilities. he said unless i'm feeling pain or am really concerned i can get some blood work done and get physically checked out, but otherwise it'l go away shortly.
he even said i could head to the pharmacy to get some medication for it (subsidized heavily through school, which is great), but otherwise it's not really big deal.
that was going back a couple years ago now, but i've had it occasionally in between for a few days in a row. more recently i've had it come back but with some discomfort. again, after a few days it just went away. i do have bowel issues that run in my family, so i'm not sure if it's directly related or not.
i don't lift super heavy and i drink lots of water, but perhaps it's the content in my diet. it doesn't occur frequently enough or cause me enough discomfort that i feel like i need to go seek professional medical treatment. i think if it ever gets any worse though i'd immediately go back to the doctor and go ahead with getting checked out though.
out of curiosity, have you been to a doctor to get checked out? if it's bothering you and you feel embarrassed about it or whatever, i'd just say get over it and head in. when i went, it wasn't invasive or anything at all, i just had a chat with the doctor about all the details and was on my way. it's definitely worth it imho.