brown coloring in my "cum" girls please

Okay so here's just an update I've been on implanon birth control since January. I bled EVERY day till May 5th then just stopped bleeding all together.I haven't bled, spotted, or even had any form of a period in over 4 months now. Well me and my boyfriend had sex recently and I "went" and then after he left I cleaned myself and I had very gooey cum that I could stretch about 2 inches or more without it breaking and my cum had brown coloring in it. And then it had brownish squishy lumps in it. The lumps in my cum where about the size of a pencil led or pencil eraser. Very small. I've had these before but they WEREN'T brown the other times they were clear and I just assumed it was my cum balling up and making a squishy ball but id describe these NEW ones as they look like when he was inside ne that he was pulling inside tissue out of me. If that makes any sense. Im trying to describe them but its kinda hard. I have no clue what this is. Im 18 and I know what it looks when I have sex and I have dried blood cone out that's not even close to what it looks like. And since I haven't had a period because of the implanon I don't have any blood up there. Hes came inside in late June then again multiple more times in July and once in august. Ive taken pregnancy test and gotten negatives but im thibking i have low levels or im not. But ive read everywhere on forums of girls getting pregnant on implanon and tgen they take tests and its negative but then tgey miscarriage without ever getting a positive test. Im scared tgats gonna happen to me especially since my implanon moves CONSTANTLY about 2" from where it should be and i have to move it back all the time and it alwsys hurts and causes pain. Ive been having every symptom of pregnancy but i didnt assume or think i was till like a month or so ago. We've also had sex multiple times since my period hasn't happen and hes cum iinside me more than once. But i dont understand what this brown stuff or etc could be. What could it be? Please help. Any advice would be greatly appreciated.