White Foam?

Hi, my cat is an almost 13 months old indoor cat, he is neutered, has had tests, shots, etc done when i took him to his first vet check up a few months ago.

I feed him all he could eat Nutro Natural Choice Chicken and Rice Meal dry food, and one 3.3oz can of Nutro Chicken and Liver Formula a day; half in the morning and the second at night. (i reheat by adding hot water and letting it sit for several minutes) It's worth noting that he has always and still does drink alot of water.

Yesterday he started making a weird noise and it turned out that was because he was about to throw up a small ammount of white foam, he did it again about 10-20ish minutes later, also a somewhat small ammount. That was yesterday morning, today in the morning he did it once again and i'm worried. He still chases his foam balls he loves and is very interested in chasing and sometimes eating flies (are flies bad for him?)

I've been told by friends that i shouldn't worry that cats do this alot but i'm still worried Help or advice is appreciated.

EDIT: He has a decreased appetite but he loves playing and jumping around with a teaser feather toy.

Cats do do this a lot, and there are various reasons for it. He could have something stuck in his throat that he's having a hard time dislodging, for example. More often in my experience, cats do this when they've eaten grass or leaves.

Why they do this is unknown -- the idea that they deliberately eat grass as an emetic when they have an upset stomach seems to be an old wives' tale -- but they do love munching on lush, green vegetable matter. You might want to make sure he can't get at any house plants that might make him ill -- somebody else will no doubt be able to advise you better on which plants they may be (yucca I know isn't good for cats). If you see little shreds of green in amongst the foam, that will answer one question.

He has no access to grass and very few leaves are around, though i did see a leaf around where he hangs out under a table.

I hear cats do this alot but i'm still very worried. He threw up ALOT just now, it was yellowish and there was a whole fly in the puddle too. It wasnt very white foamy anymore it was more yellowish color. I gave him water and he has drank a bit of water today but hasnt eaten yet and it's over 3pm. (he might have eaten before 9am when i was asleep)

Please tell me i shouldn't panic?

I wouldn't panic yet. But watch for signs of a blockage, no pooping, etc.

It could just be a hairball. Have you actually seen him vomit, so you can tell how he's behaving, moving, etc?

I don't think it was a hairball but there were a few hairs in the yellow big vomit, not enough to quailify as a hairball i believe.

I've seen him vomit yes, he just acts like any person acts before they vomit so not sure how to describe it other than that.