3 year old beagle is big stomach, big nipples,bleeding ,staying in one spot,and grunting a little bit could she be pregnant

Yes, and it sounds like she's giving birth.

I assume she is not spayed? How old is she? If she has been outside unattended at all during her heat cycle: poss pregnant, false pregnancy, or, very dangerous, has developed a pyometra-uterus fills with pus and she needs emergency surgery immediately. Gestaion for dogs is approximately 62 days. It's time to spay her at 3 years. The dangers increase with each heat cycle-pyometra as listed above, uterine/ovarian cancer, etc. A routine spay is MUCH cheaper than emergency surgery, and less life threatening!