What is up with my periods?

I have pretty irregulare periods. my last normal period was october ninth. Last month it was five days late and it was lighter than usual. normally when i have my period its heavy right away and its like the for about 3 or four days then it tapers off for the rest of the week. last week i noticed some bleeding when i was in the bathroom so i put a tampon in. i took it out after a few hours thinking it would b full like normal. but it wasnt. it looked as if my period was coming to an end. and it had that same look throughout my whole period and it lasted five days. there was some brown and bright red blood and some clots. i did have unprotected anal sex in the month of october. after my period my crampings stopped and everything was fine. two weeks after i begun cramping again like normal. my crampings have lasted this whole month of december and there still here today. the past few days my cramps have gotten more severe, and i woke up this morning with bad ones. i went to the bathroom and saw a bunch of lil brown particles in the toilet. i wiped and there was a small brown stain. i started thinking that i was getting my period so i put in a tampon. a few hours later i went to take it out to see if there was any blood on it. when i did there was brown on it and some red on it, but not a ton. most of the tampon was dry. even to right this second im having bad period like cramps but i am not experiencing any normal bleeding yet? im currently not wearing a tampon and i only have a panty liner on and there hasnt been anything on there at all. the only time i saw brown or blood was when i went to the bathroom this morning and when i had a tampon in. im hoping ill experience some bleeding later on today or even possibly tomorrow but im afraid itll never come.i took a preg test a few days ago using my first morning urine and it came back negative right away. i have no pregnancy symptoms and i dont feel pregnant. but ever since i had sex in the month of october, my past two periods have not been normal? it feels just like my periods every time but my bleeding just isnt the same as it normally is. can someone please tell me what they think this is? im very confused and i dont know wat to think. any ideas??