Hi SkinnyJ
Can you talk to anyone at work about what's going on? With your receiving medical treatment for yourself because of the strain of your situation (which I am afraid is common for a lot of carers of people with mental illness) you might be entitled to some support through work.
If you've got an approachable and understanding employer, it might be good to tell them everything that's going on as they might be able to give more support with your workload. Even if they're not approachable you might be entitled to compassionate leave (or something?)to attend medical appointments with your Dad (to share the load with your mum - give her a bit of a break?) without having to go through all the details, (just a supporting letter from your GP? Worth looking into?). I hope someone with more knowledge on your rights in this situation comes along. Might be an idea to post something in the employment section?
Even though you don't live with your parents, you are still a carer and deserve some support, especially if supporting the person you care for is impacting on your own health. Did your Dr offer you (and/or your mum) a carer's assessment? You should probably be entitled to one, but may need to ask for it.
It sounds to me as if, in an ideal world, you would like to be able to make more time to help your mum and dad out, a lot more than you find possible at the moment. Which is a positive and selfless thing to want!
I wish you every luck and the only advice I can offer is to try to think about what you would ideally like to do - get more outside support for your parents? Take the burden off you a bit? Or to make adjustments in your life so you can be more hands on in a caring role? Talk to as many people as possible about it because the strain of caring (even from a distance)is often under estimated, but there may be support available to you (and your family) that you just don't know about. Google for carers support organisations?
More generally should be done to recognise wider impacts on families of mental illness. I think it is rare for any carer not to find it hard going (I do!). IMO lack of support can often mean carers themselves need time off work, put on meds etc, so a good employer would understand the benefits of helping you early on in your situation.
Try to engage your DH in any decisions, are there any possibilities you could manage working less hours? Could he agree to putting the children to bed on regular nights of the week so you can spend an eveing with your mum? Anyone else in the family able to help out?
Over and above all you are not just feeling sorry for yourself, neither do you need a kick up the back side. You are being a very caring person, trying your best to deal with your responsibilities and supporting your whole family through a difficult time. Give yourself a hug x