Not really a teen anymore (21) but I'll occasionally pop back over here for a scroll as I lived in this forum when I was pregnant with my lg at 19.
I had to take medicine for morning sickness during my pregnancy. I was sick from 5 weeks, to about 25 weeks. Then again at 30 weeks until delivery. Without it I was incredibly dehydrated and wouldn't have been able to have finished my first year at uni.
I think that doctors are trained to assess the circumstances, and they have to decide that the potential benefits of the medicine outweigh any risks for pregnant women. Baby needs nutrients and water, and you can only give these to him/her by keeping your food and drink down.
So try not to feel too worried, and keep your fingers crossed that the sickness leaves soon! H&H 9 months xo