I understand that your boyfriend is very important for you and you would never want to lose him. I can see your deep love for him which is probably why you are this hurt. So, you will need to ask yourself some questions to find your answers you are looking for. Like...What makes you feel your partner doesn't love you ? And is there something that you haven't yet tried so that you can work on it and get him to work for you too?
1. Keep an open communication, be mindful of your mood and mood patterns (as they are part of avoiding miscommunication and impulsiveness).
2. Seek support aside from them.
3. Self-care (otherwise you may end up with good intentions that are only good intentions).
4. Constantly remember both your individual worth.
5. Respect each other's individual boundaries/agency.
6. Never force or manipulate (but instead be honest about your feelings).
Communicate. This is the most important thing in a relationship. In any relationship in fact. Think about why you think he doesn't love you, what exactly happened that may cause it and discuss about it with him. Nothing is certain until you talk about your concerns with him.
Talk to him about this. Communication is key in a relationship, and leaving these questions floating around in your head can make it toxic. If you're constantly questioning his love for you, then his repeated need to validate himself may actually make your fears true. I can not stress how important talking to him is. If you really think he does not love you, then mention this to him. Perhaps he may change his behavior.
if your boyfriend leaves you that would be more serious but if you are still together, you have him in your life to communicate and work your problems. pain is valid and you should be open and comfortable speaking the truth with him and letting him know that you don't want to lose him.