Finally sought help but what's next?

A little history.

3 years ago Me and my boyfriend of 10 years had our little girl at 28 weeks, I had preeclampsia & was rushed into hospital to have a emergency csection... The following 3 months were a blur & I think I should of sought help sooner.
O (our daughter) was born weighing 1lbs 15oz she had a major operation at just a few weeks old on her bowl, Some time after she suffered brain damage & life would never be the same again...

It's been 3 years of Doctor appointments, hospital appointments, physio appointments, speech and language, home visits, blood tests, brain scans, eeg tests, I've finally admitted I'm not ok and I can't keep pretending to be ok.

I've recently had our second baby, I'm not sure weather it's noticing now how much hard work our older daughter is, the difference between our girls or that my beautiful girl will never have a "normal," life that upsets me more.

Some days I wake up exhausted, I get up because I have to not because I want to. I'm more than happy for somebody to have our girls for a few nights and drink a bottle of wine so I can sleep better. I'm sick of dreaming about everything that happened and crying multiple times a day. I'm sick of my boyfriend asking me why I'm so miserable. I'm sick of not feeling like me and isolating myself at home.

So I spoke to my Dr who agreed it was postpartum depression she prescribed me some anti depressants (I've not yet filled the prescription) and few contact numbers, but what happens now? Am I supposed to ring when I feel low? How can I explain how I'm feeling to my boyfriend?

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