Yes,it is scary when you don't expect it.Sounds like you're in a flare .A lot of us have experience with blood.If you've been straining it could indicate hemmeroids (sp)?
If it continues to be more than you can handle,then go to your ER.but definitely contact your GIs office or GP (primary care) by Monday.It probably wont clear without Meds.possibly Prednisolone (steroids).