There are several ways to stop a breakup.
You just have to find what is going to be the best way to do it.
You and your partner are the only ones who can evaluate that and the actual state of your relationship.
Of course that you can't read the thoughts inside your partners head, but surely you can tell by his attitudes and actions.
Are you wondering "what can I do to stop a breakup"? First you can start by acknowledging that you can turn things on your favour and that is possible to stop the breakup, even if it seems inevitable.
It is very important to be conscious on what are you focusing on.
You must learn to focus on the positive.
You don't need to be the perfect person, but you must get romance back on your relationship and focus on positive aspects of your relationship.
You may do simple things like having dinner out or taking some daily time to be together to share your thoughts and feelings.
You may take bigger actions like going out for the weekend once a month or going on a trip.
The important is the direction you are taking that will lead you to a healthier relationship.
Remember to focus on all the wonderful things on your relationship and add power to them instead of focusing on the negative (insecurity, jealousy, lack of time or money, etc) so you can always see the best side of your relationship.
If you can identify the problem you can correct it, but if you are not sure, work with your partner to make it clear so you can solve it.