Implantation Bleeding or Period???

So about 9 days ago, my boyfriend and I had sex. We do not use condoms, and I'm not on BC, so therefore we use the good ole withdrawal method (he is always good about pulling out at the exact moment). 
Well, this last time wasn't as precise and he thinks "a little bit got inside of me".. 😐😐
So I didn't think anything of it, until today when I went to wipe and saw a little bit of pinkish/red blood... Also, my periods are very irregular (like as in I can go months without having one) and according to this app I am supposed to start my period tomorrow but I don't have any sort of cramps or bloating or any other sign of my period starting..
Should I be worried?? 

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