Wierd menstral cycle once we started to try to conceive

Over the past year we have been trying to get pregnant. I have a had about 4 months where I have been 3-6 days late getting my period. When this happens I can tell that something abnormal is going on with my body. I get extremely moody, I have cramps constantly for up to 1.5 weeks leading up to finally getting my period late. And my hormones seem to be screwed up much more then normal because I get significant breast pain and heaviness along with the constant aching/cramps in my lower pelvis area. When I do finally get my period it is extremely heavy and the cramps are rediculous. One of these times I went to the ER because it was so bad. I have taken pregnancy tests during these times and they all have come back negative.

My menstral cycle has always been 28 days and not severe (never late, cramping but not major, light to normal bleeding, moderate breast tenderness, moderate moodiness) UNTIL we started to try to conceive.

I have discussed this with my GYN and she sent me for an ultrasound and blood work. Everything appears normal.

Am I conjuring all of this up in my head or is there an issue here? I also have Crohn's Disease but my Gastro doctor tells me that I should not have problems conceiving based on the severity of my disease.

Please help!!!!