IUI and progesterone suppository ques. ???

I just had my first IUI done on Friday. I'm currently on progesterone suppositories.... I've had some cramping and my lower back has been sore as well. Is any of this due to the IUI or suppositories??? Or could it be implantation or ovulation?? I'm currently on CD 16. 
Also, how do I read what sizes my follicles were... D1 D2... Etc. 
Any help would appreciated for this is first "real round". First time I took clomid my follicles were t mature so it was a no go.