Miscarriage?????!! Period !!??? Help !!!!

So I've had unprotected sex with my boyfriend. He ejaculates inside me... and I'm on birth control pills BUT I DONT TAKE THEM ON TIME! And sometimes I skip a day and double up the following day.. well last night before I went to bed I doubled up ... last three months I haven't had my period.... I was worried and took two cheep pregnancy test and they both came out negative.. my boobs been tender and what not. And I've been nauseous but I also have IBS and I get nauseous with that too. And I've been bloated and I had a BIG appetite and today I've been soooooo stressed out and then I started to have really badddd cramps. So I took a shower & I had really bad pains to the point were I sat in the bathtub since my legs were feeling tingly because of the pain and then I found this coming out of my vagina? Is that a blood clot ? Miscarriage? I'm having really bad abdominal pain? Annnnd btw I've NEVER had blood clots like this ! This was really thick almost like tissue..

My periods are ALWAYS irregular even on birth control pills I have my period EVERY OTHER MONTH.. ALWAYS ... but it's been three months. I had my period since I was 15 now I'm 22. I've NEVER had this coming out. Usually when I get blood clots they are dark red, not like this. It scared me! Please any information will help?