Yes the only 1 day a week "allowance" for the relationship is a red flag, plus, is that what you need in a relationship? Did you ever want it to go further, moving in together/marriage, heck a two day a week relationship.
Obviously he has some good qualities that you liked a lot, which is what kept you two together but as he stated, he still feels like he has an "illness" whatever that is, whether it is alcoholism or he has other mental issues which he used the alcohol to cope with. No way of knowing of course but a 1 day a week boyfriend isn't much of a relationship. It may well be that is all he could cope with and finally couldn't even cope with that.
I am glad you are going to get Codependent no more as dandylion suggested, I think will find a wealth of information in there and some things will certainly resonate about this relationship.
Keep posting, I am sure you have been very hurt by all of this and it has caught you off guard and you are probably still in shock. It won't always feel this bad. Take good care of yourself, eat well (even if you don't feel like it), get in a few walks if you can, get sleep when you can and talk it out, post here as often as you like.