I stopped taking my birth control pills in May and began the same prescription, which is Seasonal where you have 3 periods a year, in September. I got a new partner in September. He is rather large. Although we have been having unprotected sex on a regular basis, I have been regularly taking my birth control pills. The last time we had sex, I had a very light amount of blood in my discharge. There was no pain involved. What is going on?

I would suggest you consult a doctor, and consider having protected sex in future, it is safer. :)
Good luck

Blood after sex can come from several factors. You could be experiencing friction from too little lubrication, your pills could be giving you breakthru bleeding, etc. His size isn't necessarily a factor since a woman is built to "stretch" for child birth... if you get my drift.

Don't forget: You've just become involved with someone... and the pill doesn't protect you from STDs.