Yes you definitely will lol!!!
No, you cannot get pregnant once you are already pregnant-post ovulation of course (hence fraternal twins)-unless you have a rare condition called Uterus didelphys (read about it here: http://en.m.wikipedia.org/wiki/Uterus_didelphys ). Once you are pregnant, you do not ovulate until you give birth and the cirvix closes & seals, so even if you did ovulate, sperm could not travel into the womb to fertilize the egg. Sex is perfectly safe during pregnancy unless you have complications and your doctor tells you otherwise. I hope this was helpful-instead of condicending.
Agreed with @elvendork. The condition is incredibly rare and I'm sure your doctor would have picked up on that on an ultrasound. A woman in Britain in 2006 gave birth to 3 babies. Two in one womb and one in the other.
Only possible is you have more than one uterus