Does anyone else suffer from irregular menustration?

I honestly hate my body for this!! I was always so regular and then when I got married and started being sexually active my body went wacko. I mean I was always pretty regular but now I never have my period on the same day or within the same week two months in a row. It just kinda comes whenever it feels it like. Sometimes light spotting twice a month.. Sometimes I will go 7 weeks without one. It is soo frustrating especialyl when I want to become pregnant. The doc did a thyroid lab test and said that everything was fine.. But I made another appt for monday so that they can seriously to something about it. For this year '05 in jan I had it the 3rd.. Then 7 weeks later on feb 24th and now its march 25th and no sign of it. I already took like 3 preg. Tests this week and their all negative.... Im soo mad.
Does anybody else have this prob????