My last period was last month and it lasted the whole four days but this month it only lasted 3 and a half days and I did not even have the brown discharge after like normal and now I am sick to my stomach like certain parts of the day even after my husband and I have sex I was wondering could I be pregnant?

Well if you're having sex, then the simple answer is YES, you COULD be.
The other easy thing to do is take a pregnancy test. If it shows up nagative, wait and take another. And then get one from a doctor if you still don't get your period.