Shortened Menstrual Cycle: Causes, Symptoms & Fertility Concerns

Question
I am 25 years old; I have twin boys (concieved naturally) age 18 months; my last cycle started on Oct. 2nd.

My cycle has always been between 35-42 days long.  For the first time in July, my cycle was only 28 days. Since then, my cycles have been between 27-30 days.  I have also started breaking out heavily, all during my cycle.  I want to try to get pregnant soon, so I have been using OPKs to determine when I am ovulating.  However, I have not gotten a positive OPK so far.  Is it possible I am not ovulating?  What could cause the changes in my cycle?  Thank you.

Answer
A normal cycle is 24-35 days (from the first day of your period until the first day of your next period). Your cycle seems to be adjusting to a normal cycle. (The cycles of 35-42 were not normal cycles and should have been regulated earlier than now). If you are having your period from 27-30 days (from the first day of one to the first day of the other) ovulation occurs between cycle day #13-16 each month. You can conceive if you have unprotected sex on cycle day #12,13,14,15,16,17, or 18. YOu can further pinpoint the exact day of ovulation if you use the ovulation predictor kits from the pharmacy to check the Luteinizing Hormone surge. Check your urine starting on cycle day #12. Good Luck.