Clear vomit no chunks?

My cats name is Doc, he is a 3 and a half year old birman and just a couple days ago he has started to vomit a few times so we thought nothing of it... but this morning he is now vomiting alot more and now it seems to be that he isnt getting anything out besides a clear liquid and sometimes a bit of white foam....
He seems to act normally when hes not vomiting though, we pick him up by lifting him under the belly and he doesnt act like he had stomach pain... very confused, should we worry?

That clearish, or white foam is often indicative of too much stomach acid and can normally be resolved by feeding them more often.   If you currently feed twice a day, maybe try 3 meals per day, one right before bedtime. 

Have you recently changed foods or is he eating a little less or anything like that?  There is usually a reason why a cat will suddenly start to vomit persistently.

Does he have a hairball? If he is acting fine otherwise wait and see if he coughs the hairball up. If he doesn't take him to the vet.

He seems fine now but im going to keep an eye on him to make sure for a day or two and I'll see from there... thank you for your help[emoji]128522[/emoji]