Guilty for recommending treatment

I can relate to each of the posts I've read on this forum. Only carers know how tough it is being a carer. I helped my partner get quick access to chemoradiation for throat cancer, encouraged him, and made sure he got to the appointments. I reassured him - but very quickly he developed extremely bad side effects including critical weight loss that has left him too weak to walk. He's mainly been in hospital since completing treatment three months ago so we've gone from being a team to him going through it on his own (though I'm there almost every day). He's frightened, angry and in pain, unable to swallow - and I'm horrified. We don't know if the treatment has killed off the cancer yet - scan due in a month, but he's battling to get over the treatment that I promised him would help. I can't stop thinking how we should have taken time and explored other options, got second opinions, and even tried some of the out-there alternative treatments that friends and family suggested – because things couldn't be worse. I know he made the treatment decision but he always trusts my advice (over anyone else's), and I always trust doctors. I feel really responsible for what he's going through and constantly guilty. I tell myself I gave him what I thought was the best advice, but it doesn't make me feel better.