I can't cope anymore

I'm sorry to say this but I just can't cope anymore with my Sen kids. I have 3 kids age 5,4 and nearly 3. My 5 and 3 yr old are autistic 3yr old is suspected ADHD too. I love my children more than anything but I'm the primary caregiver and I don't know how much longer I can take it. I'm up most of the night because they don't sleep my 3tr old trashes my house everyday, hits,kicks,headbutts and bites me all day. Hates a nappy change and lashes out. I'm a sahm my partner works 3 days a week but struggles with the kids too so he avoids having them when he is home. Family can't help as they can't cope. My 5yr old has just started smearing so I'm dealing with that most days. My 5yr old also eat/chews anything they can get there hands on and my partner has ADHD so is constantly leaving things lying around. My house is constantly messy and driving me insane but I just don't have the time to do the housework as I can't do it when the kids are around as they need constant supervision and if I do it when they go to bed I literally don't get any sleep. I'm at my wits end. Does anybody have any suggestions of where I can get help? Social services said there nothing they can do. My eldest is in school 5 days a week but my youngest is only at nursery 2 days and we can't afford more hours. My partner's just tells me to get in with it and that he can't help anymore than he does. It's really getting me down to the point I'm having suicidal thoughts and pretty convinced they'd all do better without me around. I waited so long to be a mum and had several miscarriages before my eldest was born so I feel so guilty to be feeling this way but I honestly can't take another day