I had unprotected sex in last month (dec) and I don't know whether He ejaculate inside me or not and after that I got period (dec) but now my next period (for jan month)
Is not coming is there any chance of pregnant .

Yes, you should take a test.
I had a period, though sligtly lighter, after conseption. My doctor said that I wasn't the first to surprised in this way.
Having unprotected sex will often cause pregnancy.