If you have missed your period and your pregnancy
test is positive, then you are definitely pregnant.
Pregnancy related bump does not appear so early. It only after 12 weeks that your uterus
would outgrow the pelvis and palpable in the abdomen.
If you are feeling a well defined lump in your lower abdomen then it could be due to some other associated tumor
of the pelvis.
You need to get an ultrasound
around 6 weeks to confirm your pregnancy intrauterine. The scan will also help you in knowing if your bump is not due to any other associated disease like tumors.