I’m very glad you wrote. Recognizing a problem is the first step toward fixing it. It would be a shame to end a very promising relationship like this one because you lose it for unknown reasons.
If this happened only when you are drinking, the answer would be simple. Stop drinking. Not everyone can handle alcohol. Some people are nasty when they drink too much. You may be one of them. But you say this also happens when you are sober. That suggests a more fundamental issue.
My only guess is that you are “testing” your boyfriend with your tantrums. If he puts up with this behavior, you may believe that it means he loves you and won’t leave. But as you point out, you may very well create the very situation you fear. No matter how much he cares for you, your boyfriend may understandably decide your tantrums are too much for him.
I suggest you make an appointment with a therapist to talk this over. If you are “testing”, it is probably grounded in some past experience where you felt betrayed or left. With the help of a counselor, you can deal with the insecurity and learn to trust again.
I hope you will follow through and work on this. Your boyfriend deserves better. You deserve to feel more secure in love.
I wish you well.