What is wrong with me? Depression or mid life crisis

[ChocolateTwiglet]

I'm in such a bad place mentally at the moment, I don't know whether it's depression or a mid life crisis. It feels like so much is wrong, I don't know where to start. My nice ex as i call him was found dead unexpectedly a few weeks ago and I've been devastated. Looking through old photos for his family has been really hard, its a bit like splitting up again, only worse as I'll never see my friend again. I'm questioning every single part of my life and comparing it to my 15 year old self. I'm not sure if I like who I've become, whether I've made the right life choices.

I'm so stressed, I've just worked out what I thought was an allergic reaction is actually me hyperventilating! I basically breathe really badly and don't know what to do to fix it.

I've returned to work after DC3, only working a couple of days but really not enjoying it. I'm badly managed and my professional opinion ignored, deadlines change constantly and everyone is stressed or miserable. The commute with kids is terrible, DC2 has tantrums on public transport which involve kicking other passengers. But childcare locally so expensive we'd be subsidising my job. I'm finding it reallt hard to transition between work and lookjng after kids, I spend a good few days feeling out if it after working, very distant from them and lost. I really don't think I could cope with being a SAHM mum though.

Things have been rocky with the OH since DC3 came along, they had reflux and I basically had to manage every night on my own because he couldn't cope with the tiredness. I gritted my teeth and carried on, but labelled him weak. Something died and I'm not sure if we can ever get that back again. I'm really critical of him, see him arguing with DC1 (from another relationship), falling into exactly same traps and get so mad. I've seen a selfish streak in him that I don't like and I don't think he can change.

DC1 is a fricking nightmare, suspected Sensory Processing Disorder but after 2 terrible experiences with CAMHS no closer to answer.

I make sure we have lots of fun times together - weekends away, festivals, park trips, meeting friends - but these just leaving me tireder and tireder. DC3 in our bed still so no proper sleep.

Please please help me work out what's going on!