Are these ovarian cysts?

for the past year or so ive been having really irregular periods...sometimes even 10 days late...Im always a paranoid person and since I last had sex (08/08/2008) ive been taking pregnancy tests even though everything was protected..ive taken 5 tests since then and all of them were negative(all tests taken 1st thing in the AM with 1st urine)...my period last month was really wierd all brown and clotted but lasted for the full 5 days and i got nervous BUT i realized that I had started a excessive exercise regiment and diet so i attributed that to my wierd period...anyways this month I am already 8 days late (was supposed to start my AF on 10/16)...ive noticed as of late a dulling pressure almost crampy feeling when i lean foward in my chair or when im propped up on my bed this pressure goes away when i sit or lay back tho...and once in a while ill get a sharp pain in my lower abdomen on the left side and my lower back is in a little pain too and ive been going to the bathroom to pee a bit as well i get a dulling pain when i pass a bowel movement as well as right before i pee...I was just wondering if this sounds like a cyst or should I get a blood pregnancy test.