What Causes Delayed Period/abdominal Pain After Taking I-pill Followed By Sex?

hey..doc..

I hd sex wid maa gf 1 mnth ago(8/12/2010)..she had her periods 3 days before we had sex..

but i didnt eajculate into her..

Then we again had sex on 30/12/2010..

& i ejaculated into her..

& she took an I-pill..

Her periods were supposes to come on 2/1/2011..

But she havent got any periods till today..

But she has a lower abdominal pain..

Can u suggest something to us..??