HELP!! What is this....

Ok so I'm 11DPO, DH and I done the deed tonight. I never bleed from sex especially when I'm on top. Period isn't for another three days. I'm as regular as they come. Tonight after sex I went to the bathroom as always and done the little squat/push/wipe thing to get rid of extra semen that likes to leak out. I used my towel from showering earlier. Only light on was the night light. I happened to glance down at my white towel and seen it was a bit darker than it should be. I flipped the light on and what is generally clear was pink. It's been about 20 mins and nothing else has came out I've inserted a tampon and removed it and nothing. Could this have been implantation bleeding? I have a daughter but didn't bleed. Help!