1 week ago i had a bloody stool, difficulty with bowel movements since. minor pain left side of lower abdomen. also, a vibrator was inserted in rectum during sex? how concerned should i be?

See a doctor: Without being able to exam it is difficult to answer. However you did have a object inserted and this can cause a tear at the anal sphincter. This causes pain when having a BM. The pain makes it so you do not have a full BM which causes constipation, causing lower abdominal pain. Please see a doctor for a detailed exam to make sure there is no other cause.

Very concerned: you could have a bowel perforation a simple tear or worse go to a gastroenterologist or the ER for an eval