I have been where you are. Very severely and for a long time now. I still feel it if I’m honest. And same as you with an adult child and a partner, who doesn’t make me think I’m a burden but I know that being with someone who is diagnosed major depressive disorder, plus other things that affect my day to day life really can not be easy at all.
As with you, having an adult child my mind sometimes does go to the “they don’t need me anymore and they’d get over it”, but the truth is they do need you. Still. Even if you think not because they’ve got their own life etc. But then something happens with said child and you realise they do still need you. And what I found is that what would’ve happened if I wasn’t around when they needed me? It hasn’t cured anything because mental health does t work that way but it suddenly brings into focus “fuck! What wouldve happened if I’d acted on that dark impulse I’d felt just the week before?!” You don’t know when your child will need you.
it’s not easy, it can be a constant daily battle sometimes, but ou need to realise that just because they’re adults - even if it feels like it sometimes, mainly because they’re busy with their own lives - they really, genuinely, could need their mum at any time. Statstically it is far
more likely that children of parents who suffer mh issues are far more likely to suffer poor mh too, at some point in their lives. It may not be the case with yours but actually you may not even know. I find that the kids don’t want to “worry” you with it, or their problems, when they know you may be struggling yourself (and they will know, trust me). Please try and see that you are their world, safe space, safe person. And they will need you and no they won’t get over it. I am sure they would love the rest of their lives feeling guilt.
it is hard, not going to lie to you, but you can honestly know that you do matter. To more people than perhaps you realise.
have you heard of Italk? You can self refer to them as well as being referred by gp etc. Also my local authority (county) has (county name) talking therapy. That is also covered by nhs ( they both are) and I think you can self refer to them yourself as well.
i think research what else is available in your area.
prectically, what have you done? Ie gp, ADs etc? You can go back to your gp as many times as you need while waiting for shout.