If I started my period on the 16th of one month and the next month I get my period on the 21th, am I on a 28 day cycle, if not, can you tell me

That makes sense! You'll have to double-check my math, but it sounds like you have the following numbers in your cycles:
Jan-Feb= 28 days
Feb-Mar= 28 days
Mar-Apr= 30 days
Apr-May= 34 days

With that information, I would also look into other methods of predicting ovulation, since your cycles are not always consistent. It's still important to track your periods, however.

Have you tried tracking your cervical mucus? Thought about testing your basal temperature? Tried to become more aware of your body (for instance, many women experience more sexual feelings around the time they ovulate).

There are also ovulation predictor kits, depending on how much you wanted to try to pinpoint your most fertile time.

Everything I have read say that OB/GYNs are recommending to couples trying to conceive to have intercourse at least 2-3 times per week, regardless of what week in their cycle. Others say that if you know when your fertile time is (and this can be a window of 11 days!), to have intercourse every-other day.

We have a lot of discussion about the topic of ovulation on this website, and I'm happy to share more (you can search the term "ovulation", and read other discussions).

How long have you been trying? Are you frustrated, or still in the gathering-information stage? I have tried the cervical mucus tracking, and that was also difficult for me, as I did not notice the subtle changes, but you may find this helpful to try. (No special equipment is needed, just notice the different consistency and color; your fertile time should be a higher consistency of mucus, with it being clear and slippery).

Here are some of the articles that you may find interesting:
- Ovulation: achieve and conceive
- Anything my husband and I can do to help conceive without using medications
- Fertility and your menstrual cycle

Hope this helps! Let me know if you have any other questions, and I can get back to you Tuesday. :)

Hi,

The "28-day cycle" means that there would have been 28 days between your periods.

Your cycle, for this one time, was 35-36 days in between periods (depending on if it was a 30-day or 31-day month you are referring to), which would mean you had a "35-day cycle" or a "36-day cycle". "Day 1" would have been the 16th, and then the 21st of the following month would have been the next "Day 1". (Does that make sense?)

Most women do not have "perfect" cycles; they vary from one month to the next depending on many factors (stress, medications, illness, etc).

Why are you wanting/needing to know what cycle you have?

It is best to keep track over a longer period of time, say at least 3 months, and see if your cycles are regularly and consistently 35-36 days long (counting "day 1" as the first day of your period, then "day 35" is the day before your next period...which would then start back at "day 1"). This is important to know: are you a "30-day cycle" one month, then the next month you are "35-day", or is your period more like clockwork and always "35-days"? Both scenarios are fine, but helpful information to know!