It's less of motion sickness. The closed spaces of car and bus triggers your vomiting. First try with things which don't require tablets. One solution is diverting your attention with music and close your eyes Second solution, have lemon with you. Scratch the skin and smell it while traveling. Third, have a sour tasting chocolate or toffee with you and chew it. Basically you're diverting your senses away from the feeling of fear of bus travel and car travel.