Hi Cheryl
I suspect you are not alone on this. With the cool, wet weather that northern Illinois experienced in late spring and early summer, we are seeing many crops slow in their development this year. I have a tomato plant that made it's first flower this week, when I would normally be starting to harvest.
One other possiblity would be too much nitrogen fertilizer. If you have applied excess nitrogen, that would encourage more leaf production and could inhibit flowering
