Could I Be Pregnant In Start My Period Is Brown In Color Then On The Third Day It Was Dark Red?

Brown or dark color of the periods does not indicate pregnancy. Color of the periods can change during all days of the periods and nothing to do with pregnancy. In fact a lady can have periods only when she is not pregnant because both periods and pregnancy can not occur at same time under the normal conditions. There are few ladies who can have periods during first few months of pregnancy, so, it can not be taken as general rule for every lady. In my opinion, you are not pregnant but get pregnancy test to satisfy yourself.