I know you're in a lot of pain, and it seems unbearable, but that's a significant part of life. I'm not saying it's going to get worse, I'm saying that when you learn to withstand emotional distress it makes you stronger. So the next time you're feeling depressed, your threshold will be much higher.
First, you need to be thankful for your boyfriend. If it seems that he's one of the best parts of your life. You need to fight to be as good to him as he is to you.
Second, you should embrace your feelings. They're not great (obviously), but emotions are a uniquely human quality and you should be grateful for having emotions. It's okay to feel miserable, it's just learning how to deal with them that is extremely difficult.
Third, these feelings might be a result of a physical abnormality, so I would see a psychiatrist if you're truly in an unbearable amount of distress. They might be able to diagnose a legitimate issue that you're having. It could be something as simple as a hormonal imbalance.
Fourth, if you haven't opened up to anyone (besides blahtherapy) you should talk to someone. Your boyfriend, a therapist, a dog, a plant. Anything! I lost a loved one to suicide and he didn't tell anyone how much distress he was in. He was just gone from one day to the next and it destroyed his family. This was almost 10 years ago and they still haven't recovered completely, and probably never will.
If you're not ready to open up, start keeping a journal. Sometimes letting it out in a safe way will bring you some relief. Write anything, just let it all out. Write some poetry, write a song. If you have any creative outlet, USE that. That's what art is for!If you're feeling like you need someone anonymous to open up to, feel free to message me. I've been in the exact same place you are and I know that suicide is not a solution, it's a cop-out. Everyone has the urge to end their life at some point, it takes real strength to understand that urge and resist it. You can do it, don't be afraid to ask for help.