I Hate to Bring This Up

I really do hate to bring up the awful combination of mental illness - illnesses, in my case - and a serious romantic relationship.
For the most part, my partner is understanding, supportive, helpful, just wonderful.
... But then, days like today happen.
Days where we end up in a fight because I can't do my share of things like household chores; my schoolwork suffers; my social life goes down the drain; my financial contributions are at an all time low... and that's just scratching the surface. Days where threats are thrown verbally because I can't function like a regular person. I can't function like a normal girlfriend. I can't be that.
I'm a little caught up with suicidal thoughts that bombard me, making it a feat to get out of bed, brush my teeth, take my meds, and look presentable. Let alone think about the groceries, or what needs to be cleaned, or the fact that the laundry is starting to pile up - again.
Usually my lovely partner can understand the 'whys' of all these things, but lately things haven't been easy on him, either. He has an injury that makes it very painful for him to walk, so going to work has become that much more stressful for him.. and more stress equals less patience. Which makes absolute sense... it just makes my life a little messier, because his tolerance for my limitations and affectations goes way down.
This is something I'm sure we (those of us 'blessed' with mental illness) all have to face at times, that is, if we're able to find a partner and hold down a relationship long enough to have those 'living together' disputes. I don't envy those of you going it alone - having someone to lean on is by far the superior option in my opinion, if possible -  but I feel like.. it must be nice, sometimes.. to not have to worry about what that other person expects of you.
I wouldn't trade my partner for anything, but I know how hard it is to try to be a Good and Normal Girlfriend when you're also Mentally Ill.