Small follicles on day 15

Liz • Mother of 1 beautiful and ornery little girl. TTC baby #2 since January 2012
I'm a little disappointed that after my ultrasound   yesterday my follicles were only measuring 12 and 13mm. I just finished a round of 200 mg of clomid. I go back on Monday to recheck size. I'm hoping I'm just slow to develop follicle size. We are going to attempt IUI if they develop. Has anyone else had a similar experience of developing follicles slowly?