Bloated or Pregnant?

So eve tells me i am 11 days late on my period and I was really sick last week and lost 5 pounds and almost instantly i gained that weight back in a day and a half. My stomach seems big, and i don't know if its bloated or I'm pregnant. I took a pregnancy test when i was 5 days late and it was negative. My periods are usually always consistent. But i did have unprotected sex a few times but took the plan B right away or the next day. If anyone can help me out with this that would be great. Any tips or other ways to figure this out.