I Had My Full Menstural Cycle On 8th April.i Has

I had my full menstural cycle on 8th april.i has again very light spotting on 29th april.I had brown spotting on 24th may.i went to doctor to have check up why i am having light period for 2 months.She tested me for pregnency test and my urine test is positive.i had my scanning 4 days after and they said they could not see anything.my uterine lining is 8mm.
Can you please eplain what a going through