We use the withdrawal method but..

So me and my SO use this method for over 2 years till I got on Birth Control(Pill) and got off due to very bad blood clots and it didn't help with my periods. So now we are using the method again! We had sex on one of my fertile days which was 15% and he pulled out but when I went to the bathroom I wiped it was kind of like yellow discharge(his ejaculation) his tends to look like that in the light so I'm not sure if he accidentally let some go in me or not? Don't make a difference we've already talked about if we ever got pregnant and we would keep the baby. He has a good job and I'm just finishing up school :) my CM doesn't look like that either and we tend to have 'rough sex' he goes in deep because it's what we both like and last night when I wiped I had light light brown mucus when I wiped and this never happened before to me. It's gone now and I've spotted before but it lasted for days but it's gone now!  I'm 7 days away from my period and my 15% day was 2 Saturday's ago! Don't know if this has anything to do with it but I have sore gums that are cut but I guess from brushing? Opinions??