Hello,
I took a pill on the last day of my period and it has been three days I have been taking it.
I only have sex once in a month so I take it only for 10days. Can I get pregnant on taking the pill on the last day of period? And having sex?

If you are referring to birth control pills, you can get pregnant by not following instructions and having sex.

If you are asking about a different form of 'a/the pill', then you need to be more specific.