More than likely you have started the menopause.
The periods will be erratic and you may also notice other symptoms like profuse sweating (hot flushes) at night time and also during the day. You may feel hot when other people will be fine. Bit of a problem at work when working with a group of people.
Wear layers of light clothing so that if you do experience hot flushes, you can remove some of the layers.
You may experience other symptoms too, so keep a written record of your periods and what they are like, how you feel etc.
Eat a healthy and well balanced diet with lots of fresh fruit and veg. Wholemeal seeded bread instead of white, cut down or cut out on sugary, processed and junk foods. Drink plenty of water 2 litres a day is usually recommended, more if you sweat a lot.
You may find evening primrose oil helpful, or those multi vitamins that are specifically for women entering the menopause.
It can take many years for the periods to finally stop. When you have no periods in 2 years, then you will know that you have completed that phase of your life.
If symptoms become very severe, see your doctor.
You are a late bloomer, but yes, you are in late stage perimenopause. You may not have all the typical symptoms but just know there are dozens and dozens of symptoms that connected to this time of life. Depending on your symptoms, it will determine how you treat them. More importantly, I would now get a baseline of your hormones through a saliva panel (more accurate than serum) and find out where you are with them. If you are low or high in any of them, treating them now to bring them into balance will make going through this stage much easier. Right now, because hormones at this time will be fluctuating, getting tested this month will look different than testing in a few months. As long as you are getting periods, your FSH and LH are usually not high and will not confirm menopause, because you are not in that stage yet. Officially, when you've been without your period for one year they claim you are in menopause, but I've read some women this happens to and then out of nowhere a few months later they get it again. Hope this helps.