Hi, it sounds like the guilt you're feeling is either coming from your depression or just making it harder to handle. But I'd say that no relationship is ever going to be "proportionate" all the time anyway.
As things happen in life then one or the other person is going to need more from the relationship/more support/more understanding at times.
And I'm sure you've supported your loved one's, one way or another, at times before (you may say in smaller ways, but sometimes those can matter just as much as bigger ways) and there is likely to be a time in the future when you will be giving them support when they really need it too.
As for your boyfriend he is with you for a reason (because he cares about/loves you?) . He's made that choice, why discredit him of being able to make that choice for himself, he clearly wants to be with you. If he's finding things hard that doesn't have to mean that he wants to be with you any the less. If the roles were reversed I'm guessing you might want to be there for him too, right?
But maybe if you talked to him (a bit more) there might be just some small- day-to-day -things you can do for him to make things easier on him, and you.
It is good that you're talking to him about how you're feeling though. If you're worried about him feeling a little "powerless" (?) in all of this, maybe start by letting him know, alongside everything, how important he is to you and how he can support you more (if you're not already doing that?).
And it does sound like CBT is having an effect on you so maybe give it a bit longer, considering how you're feeling. And then if it isn't the thing for you then you can always try something else.
Best wishes
Alison