Suggest Remedy For Irregular Menstruation

i have a couple questions can you help me if possible please? i had a period march 2 2010 they last 7 days 28 day cycles and i have missed mine in april i had 3 times were i just spotted a dark brown color and then two that was a very light red! it wasnt 3 days in a row it was more of a spreaded out and they didnt last all day i have done urine test and went to the dr and done a urine test and it came back neg! i have pcos and my periods have been regular and hormone levels are low so what should i do to find out if i am preg?