Pain after sex and blood clumps?

okay so for the past few sex sessions, it's been really good and perfect, but a while after (sometimes minutes, hours, and once even a day) i'd get intense cramping from my belly button down. even just orgasming alone. i just went to the health department yesterday and took a pregnancy test that came up negative. but for the past hour i've peed more than twice, and just a few minutes ago barely any came out but this time a couple stringy red clumps came out. it hurt where the top of my pubic area is. my pee also smells strongly of chemicals. is this normal?