If your girlfriend has lost interest in you, you need to try to get her interest back. If you have been dating for a long time, then you probably know what she loves. So try to play on this. If the girl has grown cold, then you can:
1. to take to the movies;
2. go to a concert together;
3. go on vacation;
4. just be together more often.

Of course, there are many ways, and who knows the girl better than you, therefore the recommendations are often individual. Just try to be together more often, because girls like no one else love affection and attention.
When a young man is fixated on his problems, work, study, some kind of family showdown, then he forgets about his girlfriend. To prevent this from happening, it is necessary to constantly maintain the girl's interest.
Write her a few SMS, make a small gift, just put things aside and be alone. Business will not run away, but it is easy to lose a girl.
When your girlfriend is missing something, she will still inform you about it, maybe not directly, but in hints. Listen to her words. If she wants to relax with you, then she will say that she wants to go somewhere, or she will tell you how her friends rested. A person never says anything just like that, he is always projected through speech. If he is waiting for attention or help, he will definitely say about it.

ATTENTION AND LOVE DO MIRACLES
There is no need to dismiss the girl, considering it whims, to assume that everything will resolve itself. Usually such problems do not disappear, but girls disappear and find more attentive gentlemen.
Some girls lack warmth, hugs, kisses, sex, so think, maybe this is the reason.
You can talk directly, ask what does not suit you in the relationship. When the problem is sore, the person will tell himself, without coercion. Often, when a man does not have specific goals or he keeps the girl in the dark about them, a conflict can arise. Place all the dots over the "I", voice your plans, and, perhaps, the girl will feel better.
The easiest way, of course, is to try to return romance to a relationship, this is the most tried and tested way. Do not insult and humiliate a girl, she will never return to you if you act in this way. Only tenderness and affection can achieve what you want.
It happens that a girl falls in love with another guy, and while everything is in full swing, you can still do something, but then it will be too late. If you do not want to change, then the girl will quickly understand that you have deceived her, and will no longer believe you.
When you feel that the limit has come in your relationship, and nothing is helping, it may be better to part, maybe for a while, maybe forever. Each of you will assess the current situation and draw the necessary conclusions.
It happens that the relationship has already outlived its usefulness, and there is no point in clinging to them.