Some help/advice

ok sorry new to this I'm on the implant have been since November 2015 and I'm in an active relationship. On Tuesday last week I was given antibiotics to take to get rid of a urine infection(symptoms had gone within a day). I had unprotected sex as I usually do with my partner wasnt sore at all. The next morning I started spotting brown/pink/red blood. The 2nd day I didn't see anything on my pad but when I wiped I saw brown blood then 3ts day got a bit heavier on the 5th day looked like it was finnished but then yesterday I started bleeding dark brown blood which was a bit more wet/runny(sorry tmi) I just wondered if I could maybe be pregnant even though I have an implant in? I have 2 kids already but don't remember this happening befor. I took a hpt a few days ago but thought it was slightly too early to test. Any ideas?

Thanks in advance 

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