My cat is sick? Help?

My 8 year old cat Spike is sick. The other day he threw up liquid vomit all over my couch, then this morning I found large vomit chunks all over my room. Maybe 3–4 piles. He usually eats wet food, but I ran out and gave him dry food yesterday afternoon and evening where I usually feed him wet food once a day. (if maybe this has something to do with it.) Well I also noticed along with him throwing up he peed on my bean bag chair, and he started to try to diarrhea on my carpet but not much would come out/a tab bit of blood was in it (this also has happened his whole life, but not that much). I have a vet appointment at 2:45 this afternoon but I’m really worried and I don’t know what could be wrong with him. He has peed on the beanbag before when his litter is dirty but today his box was pretty clean. I also had him checked for diabetes almost 2 months ago because my other pet had passed away with undiagnosed diabetes and I don’t want to relive that. Can anyone please help?