I'm still losing weight !

I'm already in my second trimester I'm about 15 weeks and I'm still throwing up and the medicine my doctor gave me isn't helping. I've only lost weight during my pregnancy and I'm concerned. What did you guys do when you couldn't hold down food ? Should I be taking other supplements? What are the best vitamins that won't make me super nauseous? This is my first pregnancy so I have no idea what to do and my doctor is basically telling me to just deal with it and that it's part of pregnancy