Why Are There Lymph Nodes Getting Swollen In The Groin And Neck?

About 3 years ago I had a lymph node inmy groin swell up it was just one then but now I have multiple lymph nodes that are swollen and now in my neck as well... they are getting bigger and they do not hurt.. I also have been dealing with a rash on my belly that doesn t itch and ulcers in my mouth that are very painful for 5 months now.