What is my loss of appetite?

I haven't been eating much these past few days. I have dry mouth but I drink plenty of liquids.. In fact, I've been drinking a lot of juice and water.. I rarely ate breakfast and lunch, (I know that's bad but I was never hungry enough. But I always ate plenty at dinner and over the weekend.) these days I'm barely eating at all. And when I do I eat I get dizzy and nauseous and really tired and need to lie down. I also get grumpy after i eat. Without food I'm fine though. I'm energetic and happy. I drink milk with a nutrition powder in it some days. But only a small glass and only sometimes because most of the time it's too rich for me... I'm a little worried. I'm losing weight and even though I'm still at a healthy weight ( i've only lost a little and I was a tad in the heavy side of the healthy weight zone to begin with), I don't want anything to be wrong... I love food and want to eat but I feel sick after so Ive trying to eat as much. I am on meds that would induce weight loss and appetite loss, but ice been on them for months and this is fairly new in the past week or so... I did feel good after eating an apple tho... My question is, what could be causing this sudden lack of appetite and what foods could I possibly eat that wouldn't be too rich for my weak stomach.... I haven't gotten sick yet, but Ive felt like it and I'm trying to avoid it... Thanks...