Assalamoalaikum,
We were both asleep, sleeping at a distance, when I realized my husband wanted to have intercourse. He had been very busy for the last few days with office work. So it had been some days since we last came close. I had told him about 2 or three days back that I had my period. I only have occasional spotting after the first 2 days of my period. I found him so desperate, that I also got carried away and just could not stop him. I had not had any bleeding since evening, and got only a little spotting the next day, almost after 24 hrs. my husband also wore a condom during intercourse.
I am feeling extremely guilty since that night. Does it effect my nikkah? Is there any kaffara I can pay?

I request you not to publish this question or any information about me on the website.
But I don't know how you can answer then. Maybe just give the question title and the answer.
JazakAllah.

The reason why it is forbidden to have intercourse with one's wife when she is menstruating or bleeding following childbirth - islamqa.info (http://islamqa.info/en/43028)

Sex during menses and spotting. - Encyclopedia of searchable Islamic Q & A - Islamhelpline (http://www.islamhelpline.net/node/8091)

Sexual Intercourse in the state of Menstruation (http://www.inter-islam.org/Prohibitions/mensesinter.html)

https://en.wikipedia.org/wiki/Islamic_sexual_jurisprudence#Menstruation

Was it spotting, or were you still on your period? Spotting happens sometimes for days or even weeks, in between and after periods. Spotting doesn't mean you were still on your period.