Your Hair Is Growing, But It's Not Getting Longer
There are two primary reasons for what you're experiencing.
One: your hair could be enduring continuous damage that is chemically or mechanically trimming it (I'll explain this below).
Or, two: you have reached your genetic max length and need to realistically consider your options.
Mechanically Damaged Hair
If you are using a heat tool on your hair every day, you are most likely melting it. Using heat protectors helps, but some products that present themselves as heat protectors are terrible at their job. There are two tell-tale ways to check to see if your hair is melting. Grab a section of your hair, usually the top crown area or your front hairline area. Pull the crown section straight up off of your head toward the ceiling or the front straight out in front of you along your cheek bone. If it looks severely uneven and the ends feel rough and crinkly, you're burning it. If the ends of your hair look wispy and thin, then you're slowly melting it.
There is nothing you can do about burnt or melted hair. You don't necessarily have to cut it all off all at once, but you do have to change your routine if you want it to stop. If your hair is fried, you can see it break off in little pieces when you comb it. Come in for a trim and invest in products that will get you past this point and stop future damage from sabotaging your hair growth.
Chemically Damaged Hair
If you or someone else has been using chemicals on your hair to alter the color or the texture, then you might be chemically trimming it. Once you push your hair past its breaking point (no pun intended) not only will it disintegrate, but it won't even take color anymore. You know this has happened to you if your hair feels mushy when it's wet, if it takes a long time to dry, and has fine little matted areas. The smaller circumference of each individual hair, the easier it is to damage.
You're not genetically able to grow your hair that long
Since I fall in this category, too, it's lucky for us that technology has reached a point where a shampoo and conditioner can help your hair grow longer and affordable extensions exist. I use both and, unless I tell someone, nobody knows it. Kevin Murphy makes a shampoo, conditioner, and elixir that use the same technology as those lash growing products (something I use and swear by, too).
Use Kevin Murphy's Plumping line it every time you wash your hair. If you alternate with a different shampoo and conditioner, then at least use the Body Mass spray on your wet hair and scalp as directed. Give it 6-8 weeks to see some growth, and remember that once you stop using it for a length of time, it stops working.
If you would like to discuss hair extensions, book a consultation and your stylist will tell you what to expect. It's 15 minutes and it's free.