Excessive Vomiting

I am currently 8 weeks pregnant. Been vomiting quite a lot lately. And today I have vomitted for the 3rd time. Starting with the Milo drink that I drank, the pau that I ate abit and yellowish stomach acid. And the 4th time followed by white foamy vomit. I have gotten anti nausea pill from KKH but apparently I still vomit after taking it. When I should I really start to worry about this excessive vomiting and go to hospital straight?