I had a period for sure on Sept 18 and on Oct. 15 I spotted for 3 day I didn't have to wear a pad because it was only there when I wipped. In Nov nothing at all I took a home pt it said I was pregnant but I'm not sure how far along. Do I count what I got in Oct as a period?

How far along you are is a best guess, even if you know exactly when your last period was.

An ultrasound (when you're further along) will be able to give you a better idea. But even an ultrasound is a best guess.

Are you worried about dates because it's a question of paternity? If that's the case, then only a DNA test after the baby is born, can determine that.