Occasional pain & swelling of scrotum

[tem123]

Every so often (anywhere from a couple of times a month to once in a couple of months) I get a swelling and a pain down around my scrotum. This usually takes up to half an hour to happen, and when it does, my left testicle aches, there is a lump above it, it hurts to bend down, and I have a pain in my stomach. On two occasions this has been accompanied with nausea. It can last for minutes or hours. So far I haven't been able to notice anything in common every time it's happened, in terms of working out what might have caused it. The closest thing I've found from browsing online is an inguinal hernia, but that appears to be worse than what I'm getting. Any ideas?