What Can Be The White Chunks That Come From Penis After Squeezing And Pushing Hard ?

Hi, may I answer your health queries right now ? Please type your query here.. Yesterday i had sex for the first time in a while and i pulled out and squeezed my penis so it wouldnt shoot seamen at my partner. this afternoon i had solid white chunks follow up after peeing at work. then when i got home i sat down and pee'd again but i pushed hard and it felt like something discharged and then a bunch more white chunks followed. i was also just recently tested for most std's and was told i was considered to be clean. what can this be?