I have swollen lymph nodes in my groin, armpits and neck. groin is most painful. also have bloating and slight nausea. so worried, what could this be?

Need check up: The cause is probably nothing serious, most likely a viral infection, but you need to see a doctor to go over your history, examine you, and make sure you don't need other tests, indicating something more serious. Do go in for a check up.

Monitoring Centers: Lymphatic system absorbs/carries things too big to go into the arteries/veins like bacteria eaten by white cells/digested food. Lymph nodes "taste" the lymph everywhere for bad stuff like bacteria/viruses/cancers, etc. When it detects a problem, it alerts the immune system and your body reacts. They enlarge in response to the inflammation they create when they react. They shrink when all is well.