Had sex during ovulation week. period started a day early, and only lasted 3 days and was light n watery. had pregnant symptoms ever since..could i be?

Possibly not likely: Early pregnancy can be checked easily by a pregnancy test. Current over the counter tests can in some cases (look at the label) determine if you are pregnant as early as 6 days after ovulation. It is not likely that you are pregnant given your symptoms, however. Check again in a week or two and if you want to be pregnant, plan and be healthy. If not, protect against it!