I've had a lot of pressure in my lower abdomen, after 3 weeks i had a strange bm;long gray brown worm-shaped string w/white 1in masses attached to it?

Unusual: Hard to say but I suggest you see your provider and have a stool test looking for parasites. This may be nothing but it is best to have it checked out.

Need check: Gastroenterology, perhaps check for ova and parasites? Any international travel, any unusual diet? Any bleeding? Any other illnesses? Jaundice? Liver issues? Full history and physical and colonoscopy should solve the issue