Angel,
you state symptoms but give no information that would help us help you.
Like your age might be the issue - my impression is of a young girl - so could it be hormonal - either to do with first getting periods, first sex or possibly being pregnant?
Or are you going through some major life changes - family break up or loss, school ending & new unknown life starting or major exams scaring you or moving house to another town or whatever??
Have your eating patterns changed? What is your general health like (same or diferent to before this started? You say this has been lately but how long is that in fact - 1 week, 1 month, 3 months?? Has anything like this happened to you before or to anyone else in your family??
In the meantime you could try some basic "coping" techniques like - when you start to feel overly emotional take some deep breaths, go do something else somewhere else, use imagery so practise imagining a really peaceful scene & keep practising bringing that scene into your mind (start learning this when you aren't all emotional!!) something that you find relaxing & restful something that will help you calm down & feel good. You might also get a dvd or video of yoga which has both exercises & meditation this could also assist you - some of the exercises are also good for nausea.
You might also consider when/where this happens & try to avoid the situation/place if possible or at least to prepare yourself for it if you can't avoid it.