Stopped birth control ready for baby #2

Jasmine
I was on the patch birth control and I stopped putting it on 4 days ago. I got my period 2 weeks ago and I started spotting today. My fiancé and I had sex yesterday, and I was wondering if anybody knew if it was the lining shedding because a sperm made it to the egg, or just because I stopped my birth control? This would be baby number two who's almost a year old! Thanks in advanced :)