Is it normal to be irregular at 43

Yes, you're getting to the point where your body is starting to shut down the child bearing equipment.

That's not always true you may not be going into menopause it is very normal to have irregular periods at any age for no reason but some reasons could be change in exercise, eating habits, the medications you are taking, and even stress can cause irregular periods

It's possible that you are going through perimenopause. This is the pre-menopause period. Your periods may be lighter or heavier, last longer or shorter, yet be very irregular. Once you don't have a period for a year you are considered in menopause.