All signs point to it being yours. If you still arent convinced, go with her for her first ultrasound. The doctor will know approximately how far along she is, so you will know, for sure, that way.
DNA test and some councling maybe?
It depends on the cycle. No women do not have full periods during pregnancy but they can bleed when they are supposed to be having a cycle. First, was it a full cycle or lighter than usual. I would get a test done if you are worried, but if you love her and the baby is yours in your heart then it really doesn't matter now does it. Do what is best for you dear.
If she had her cycle in September then that would be an indicator that she was not pregnant at that time.
Im not a dr r anything lol but my bro was thru the same thing they where on a break his gf slept with someone else he couldnt shake the thought that she wasnt his. But she couldnt look anymore like him. The dates added up to be his but to save rows and throwing it up in the gfs face they done it and suprise suprise she was his so go with your gut love and best of luck xx
Btw im not a doctor r anything its just my wee bro has being thru the same thing dates added up dat it was his but he still couldnt shake the thought that she wasnt. So a dna was done even tho she couldnt look anymorelike her daddy lol. N suprise suprise she was his also he didnt wanna keep rowing with the gf and throwing it in her face so it had to be done and she was his they regret taking that break now because it near ruined them. But best of luck and congrats xx
If she had her september cycle its ok because that was after she cheated but if your having doubts theirs always a dna. And maybe that would put your mind at ease but by the dates you gave its working out that your the father. Because theres no point you thinking the whole time if its yours are not. Xx