My cat threw up all over the house last night

I agree. You should consider taking your cat to the vet, just for peace of mind. Another thing to do is to avoid giving him any more milk. He may be allergic to it; give him fresh water daily instead. You should also know that cats do puke every so often for whatever reason, and it's annoying when it happens. And why they have to puke on rugs especially is beyond me and a subject for another topic. If I feed my cat, Mimi, chunky canned cat food, she will most definitely upchuck it, so I avoid giving her anything like that and she's fine. My Columbus cat will regurgitate every so often; mostly it's spit-up rather than vomit, but still a nuisance to deal with when it happens. Cats lick themselves and throw up from having too much fur on their tongues or in their throats.

I don't think milk is so good for cats to drink. But I would definitely get him checked out, to see if he's alright.

The excess throwing up sounds like he is ill. I would take him to the vet if I was you.

Oh man that is bad...I feel sorry for your cat and you...your cat because she/he is sick and for you having to take care or him/her and cleaning up the mess everywhere...