Yes I am 20 days late on my period I have taken 2 pregnancy test both which have been negative the bottom of my stomach is swollen and very bloated. I am also having trouble sleeping and sharp pains in the stomach. Could I be pregnant?

You aren't going to get ANY change in stomach size for at least 4 months. It takes that long for the Fetus to grow large enough assuming you actually are.

When exactly are you taking these tests? First thing in the AM , the FIRST time you pee that morning?

Are you taking the test, first thing in the morning, as soon as you wake up. With first urine of the day?
For best test.

But yes, some women will show negative, till even 4 week or more late. You can go into the doctor for a blood test to confirm.

But agreed, you should not be seeing any real change in the body at this point.