Hello I Think I Am Misscarrying... The Last Time I

Hello I think I am misscarrying... the last time I had sex was January 11 and 21st. and today I started bleeding.. i have never had cramps but they were so bad today I had to leave school.. I'm only 16 I'm on no birth control nor do I use protection. I went and got a a 2 pack pregnancy test and the first one was positive then 1.5hrs later I took another and it was negative. my blood started out as a brown/red and very slimy then after about 2 hours it was red and kind of clumpy then sometimes it looks like jelly. also using a tampon is very painful.