If you are noticing that your periods are spacing out or otherwise changing in their pattern, that is definitely something that is worth talking about with your primary care doctor
or your OB GYN doctor. There are many different factors which affect timing of the periods, and therefore most women will, at one point or another, notice some irregularities in their cycles. However, if you are noticing an emerging pattern, or if this is beginning to occur more often than not, then it is worth getting checked out.
The main issue that your doctor will want to investigate is whether or not there is a hormonal imbalance that is causing your menstrual irregularities. For example, alterations in the function of the thyroid gland are a very common cause of menstrual irregularity, and there are often other signs as well that suggest thyroid disease, such as fatigue, changes in the skin or hair, or changes in weight.
Another very common condition which which alters hormonal balances is polycystic ovarian syndrome, which occurs when the ovaries produce elevated levels of male sex hormones. Other things that might be signs of this condition would include obesity, elevation of the blood sugar levels, or increase hair on the body.
Your doctor will be able to help you figure things out.