male cat puking two days in a row!! :(

My unneutered male cat, Indie, started puking about two days ago. He had something to eat and straight after that he began puking -- about three times in a row. It was a brownish colour and kind of looked a little like tuna fish. He slept all of yesterday, but would get up to do his routinely 'patrol' that he does every day. He didn't eat anything either :/

And last night be puked twice again, this time a clear liquid. He's much more active than he was yesterday and is yelling and being as playful and active as he usually is!! He also had slightly runny poo yesterday morning and I'm really worried about him. I'm tight on money at the moment too, plus the vet I know lives an hour away and I don't want to give Indie any stress that he doesn't need...

Any help would be GREATLY appreciated, it's really urgent :/

Additional Info (if you need it?): He's a tabby cat and is roughly 1.5 years old. We found him as a stray as a kitten and brought him in. He pukes about once a month normally, and I haven't actually seen him have a fur-ball yet, could it just be that? He's also a pretty slender cat, and always has been despite having two meals a day. I think it's because he's active? If anyone's got any advice that'd be great!! He means the world to me!!

I understand being tight on money (BELIEVE ME, I do), but you probably want to take this guy into the vet as soon as possible to get checked out. At the absolute least, you should call your vet and ask their thoughts. So many things that could be causing the problem.

Did he eat anything he shouldn't have recently?

I'm going to try and get him into the vets sometime this week ;-; I just ope they're co-operative, ove here they're pretty much money snatchers and handle the animal so terribly... I'm so worried about my little boy I don't want to take him in and have them make him worse...

The only thing I can think of is that he ate a fly the night he started puking? He's a completely indoor cat so I don't think it could be parasites either? My other cat is completely fine, no puking or diarrhea, touch wood!! He's also an unneutered male, though a siamese instead. I was thinking maybe he could have IBS? But we haven't changed his diet lately, he's been on the same thing all his life... It's just this year that he started puking though (well these last 6 months)

Update:

Indie's doing much better!! I made him a meal of boiled rice and chicken and he downed that well!! I'm thinking he's just got IBD, because everything else is alright... there's no bloody stool/vomit or anything of the sort. He's also active and being as stupid and loud as ever lmao. He hasn't puked since though his stools are a little watery. I'll keep him on the rice/chicken for another day or so and he'll hopefully be fine!!