The trouble with Pandora's boxes is that whatever is inside does need to come out. And will push to come out - at times that may not be convenient to you, but at some point you have to listen and let the lid come off.
Gestalt counselling I find really weird as a concept - try humanistic counselling instead, that's more about communication - although it isn't the counsellor who needs to do the talking, they mostly reflect back to you what you have said and try to lead you on from it - so the jokey sketches about "and how does that make you feel?" are about right - but the idea is that rather than just reacting to your feelings when things happen, you examine them and see what's going on - this helps you to adjust better.
So when you're in a very low place, which it sounds like you are heading towards now, that is the time that the lid is pushing to come off - and the best time to take it off, clean the wound and start to heal.
If you are seeing negatives in everything, all around you, then your DP is part of that pattern too so it's unlikely that you can think much positive about him either.
Try this idea for size - and I don't think this is the case, necessarily but it might resonate - you think you are a bit pathetic to still be depressed; you cannot understand why your DP puts up with you and therefore he must be either desperate or a bit thick or just unobservant - he can't possibly really love you because you're so miserable and angry all the time, so what kind of loser does that make him, if he stays with you? And do you want that kind of loser to stay with you?
I'm not saying that's you at all - but it might be, it's the sort of thing that can badly affect relationships (my sister suffers from the above scenario) - and it can be down to your own low self-esteem, as it is with my sister. Fix your own issues and then see whether or not it changes your opinion of your DP.
Remember too that depression is a grey/black gauze that colours everything you see - once it lifts, things show in their true colours again and they might be much brighter than you think now.