What Causes Irregular Menstrual Periods?

Gooday, i have been married since dec. 2010, i am healthy but 2 years ago i did a hormonal analysis and i foundout that one of the homones was high which was progesterone, the doctor prescribed parodel (bromocriptine mesylate) which i took for 2weeks, but i have noticed that sometimes my menstral cycle is irregular, it always late such that i thought i was pregnant , by january this year it was one month later than usual, this month is also 10day late i had all signs of pregnancy but went for test it was negative , pls i need to knw what i will do? to regulate my cycle, and also get pregnant. thanks